I'm going to come at this a little differently if that's ok
With a $2000 budget for a projector, surround sound, and let's not forget about other important things like power protection (a battery backup for your projector bulb is a MUST in my book!), cables/wire and a screen! Trying to get all of that on a $2000 budget, I'm of the opinion that it's better to not try and make this a "dream" system, but rather, to come in knowing that you're going to have to compromise and sacrifice a little bit and thus, go with speakers that are very good for what they are (cheap

), but aren't trying to pretend like they're bigger and better than they are!
So here's the system I would put together with a $2000 budget:
Projector:
Epson Home Cinema 8350: $1150 - looks like you already found this gem! No better choice in the under $1500 price bracket. Really excellent. You won't be disappointed

I'm not sure where you found that $1000 price though. The lowest I'm seeing is about $1080, with $1150 being the going price on the most reliable internet resellers like projectorpeople and amazon. So I'm going to play it safe and give it a $1150 price tag.
Battery Backup UPS Power Protection:
APC Back-UPS ES 750 (BE750G): $80 - As I said, I consider a battery backup UPS (uninterruptible power supply) to be absolutely vital for any projector or DVR. Everybody gets a power outage from time to time. If it happens while you have your projector on, it can seriously shorten the life of your bulb or even cause the bulb to explode! That's because the cooling for the hot bulb instantly shuts off if the power goes out...but not if you have a battery backup! APC is THE go-to company for power protection. The Back-UPS ES 750 gives you 5 outlets with battery protection and 5 other outlets with surge protection for less vital gear. The battery life isn't all that long if you have your gear up and running, but the idea isn't to keep your whole theater going during a power outage; the idea is simply to give you enough time to safely shut down your gear, allowing your projector to go through its proper cool-down cycle with its fan going. And if you have a DVR, you can keep your recordings going for a while. Might not get you through a long black out, but if the power's only out for 15 minutes or less, you can keep your DVR running and not lose your recording! Must have, IMO.
Receiver:
Onkyo TX-NR609 or Denon AVR-1712: $400 - I like Onkyo myself. They really push out the features for the price. But their customer service SUUUUUCKS, so if you happen to get one of their hot-running units, it's a pain getting it fixed or replaced. The alternative at this price point is the Denon AVR-1712 and it's pretty competitive feature-wise. What I would strongly recommend is that you go to onkyousa.com and denon.com and download the manuals and read through those. You can't really go by the specs and features that are just listed on the product pages because those are often inaccurate. Read the manuals instead and that will fully detail the features. If the Onkyo has a feature that you really want that the Denon lacks, I've no problem recommending the 609. Where Onkyo really shines is at the $600 price point where the TX-NR709 is the least expensive receiver out there to offer pre-outs for all speakers. To me, that's an important feature because it means that you can add separate amplifiers in the future if you want to. But with your budget, $200 extra is a lot, and either the 609 or 1712 should be just fine for what you need
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So, at this point, we're already up to just over $1600. That leaves very little room for speakers and a screen plus cables and wires. If you were trying to get honest-to-goodness great speakers at the lowest possible price, I'd be telling you to spend at least $350 (more like $550) on the subwoofer alone! So I think your best bet is to put that kind of idea completely out of your head for the moment, and instead, focus on the idea of getting "pretty darn good sound - amazing when you consider the price"! The type of speakers that you can easily and happily upgrade one day in the future because you spent so little on them. And speakers that are still good enough that they wil impress you now and then, one day, easily move to another room or sell for very close to what you paid for them originally! I give you...
Speakers:
Onkyo SKS-HT540: $260 (at Amazon) - these are, hands down, my absolute favorite extremely low cost speakers. They are surprisingly good. To be perfectly honest, throwing price out the window, I would take them over the Polks that you were considering and put them just a fraction down in performance compared to the Energy 5.1 packages that I consider to be the best out of the list of the candidates that you listed.
Honestly, if you are limited to around $500, I say that it is not worth it to spend $500 unless you want to get just a single pair of good bookshelf front speakers. Instead, spend half that on these Onkyo speakers. The Onkyo SKW-204 subwoofer that comes in this package constantly makes me smile whenever I hear it. It's no Rythmik FV12 or HSU STF-2 - let's be clear about that! But for around $110 on its own, it's an honest-to-goodness little gem that thumps its little heart out and just puts to shame the subwoofers that you'll find in most of those $500-ish 5.1 package systems.
Bottom line is that if you want to spend $500 on just a pair of front bookshelf speakers, that's a good way to go. You can add the subwoofer, surrounds and center (I'd go in that order) later and get a very good pair of speakers for now.
But if you want surround sound right away (and 7 channel surround at that!), you absolutely cannot beat the SKS-HT540 package. THIS is the way to do surround sound speakers on the cheap. Instead of being disappointed and feeling as though you want to upgrade almost right away, but paying a full $500 or $600, which isn't chump change, you can pay a mere $260 and be darned impressed! At that price, it's awfully hard to feel disappointed when you get sound quality that is actually pretty darn good. At that price, it's easy to justify an upgrade in the future because you paid so little right now! And at that price, it's easy to sell them later or just use them in another room.
On your budget, this is what I would buy - no question. Check out some reviews online if you need more convincing

One thing to note - the Onkyo SKS-HT540 speakers are actually physically larger than you might expect! Onkyo's OEM didn't try to overcome physics with "magic", marketing and lies. They just put together honest speakers with inexpensive parts and you get the rewards of just plain, simple design. I hope you go with these because, to me, the next real price bracket for a 5.1 speaker set starts at over $1000 where you're spending at least $350 on the sub alone and around $750 or more on the speakers. Below that price point, it's compromised-performance city. So if you're looking at compromised performance no matter what, why not spend as little as possible? Why spend $500 when you can get the same performance - actually BETTER performance, IMO - spending only $260? It just makes sense, and I hope you'll agree
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So after shipping is included, we're probably close to around $1900 now. That doesn't really leave you enough money to get a fabric screen of any kind unless you really can find that 8350 for less. If you can, or if there's a little "wiggle room" in the budget, my favorite low-cost screen is the Da-Lite High Power with either Da-Lite's least expensive frame, or better yet IMO, their "Model B" or "Model B" manual pull-down screen case. When it comes to transportability and easy installation, nothing beats a manual pull-down screen. Da-Lite's High Power fabric is really excellent for pull-down screens. It hides any "waves" in the fabric, which always crop up with a non-tensioned screen. And its high gain gives you image a huge "wow" factor, with a really bright, vibrant image that you can even watch with some ambient light.
Finally, for your cables and wires, you will, of course, head on over to monoprice.com
So that's that! The keys in my recommendations are the APC Back-UPS ES750 battery backup, which I really think is vital, and the Onkyo SKS-HT540 speakers, which are just a steal and the way that I absolutely think anyone should go for a full surround setup unless they have over $1000 to spend on speakers.
Hope that helps!