You mentioned Elacs? If you watch prices (or set a watch on a site like camelcamelcamel or whichever you like) you can find the UB5 for as low as $300 per pair on rare occasion (I think that was a one-day flash sale). More often around $350. You definitely don't need to pay the full $500 if you're willing to watch for sales. However, you JUST (literally ended yesterday) missed a bunch of Elac sales. Not sure when they might recur.
There are some who actually prefer the cheaper B6.2 to the UB5. I am not in that camp, and feel strongly about that position (unless maybe someone wants to literally put them on/in a bookshelf and needs the front port). I very much like the UB5, and somewhat dislike the B6.2.
However, I continue to find that 4-ohm (ish) speakers don't do well with some inexpensive amplification. I did not find the UB5 to pair well with either the inexpensive Topping MX3 or the NAD D3020 v2. Not only was it harder to get them loud enough (and I'm not one to play things loudly), but they just didn't sound very good, as opposed to when paired with something with more power like the Outlaw RR2160 or a decent home theater receiver. (Yes, I actually tested all these, and did level-matched A/B comparisons with some older KEF and Paradigms before deciding to keep the UB5s.) I hesitate to recommend the cheaper Micca RB42 speakers to anyone on a budget for similar reasons - whatever you save on the speakers you're going to have to spend on the amplification just to get them to sound good, and many seem to think that's the wrong way around.
I think the UB5 go decently low for their size and price, though bass hounds might disagree. Obviously, like any bookshelves, they do benefit from a decent sub. They sound pretty neutral and measure pretty flat - if your experience leads you to think you'd like that, I would recommend keeping them on your shopping list. (You might be able to hear the B6.2 at a Best Buy, but I think they sound pretty different.)
There have been some other threads about inexpensive floorstanders from a few companies lately - if you look at recent threads you'll see them discussed. I don't have experience with those.
The Polk LSIM 703 may still be available on sale for about $450-$550/pair, depending on the deal (somebody mentioned Slickdeals and Adorama). I also like those, and I feel like they go lower. They are pretty big/heavy for bookshelves.
I'm not sure what to recommend for amplification in the $500 range. If it's home theater, probably something like the Denon X3500h, but if it's 2 channel, I'm not sure. Others may have recommendations. (I continue to be suspicious of all inexpensive class D digital amplifiers, because I'm yet to hear one I like much. But good ones may be out there.)
