There's nothing wrong with shopping around.
Mike: That should be plenty of power. While the Yamaha speakers aren't the most efficient in the world, the 757 (or the the equivalent receiver over there) will be fine. I have an old 70's Yamaha receiver that I'm using to drive some BIC bookshelves and this thing cranks out the sound. At levels where I have to put on hearing protection to get close to the speakers, I'm only seeing 50 watt peaks. Then note that Yamaha has a small horn design on their speakers and you can see that the 100wpc on the receiver should be plenty.
Benolium:
Yes, using two 333 speakers in the surround rear channels is how you would do 7.1 sound. The only reason you would use a 444 in the rear would be as the Rear Center speaker in a 6.1 setup.
As far as the system you're looking at...
If you like the Klipsch horn sound, then that's great. I don't but whatever. HOWEVER...I would look at the Reference series of speakers. The Synergy line is kinda...sub-par for the amount of money you spend. If you really like the horn thing, then I strongly suggest that you check out the Acoustech line from BIC. You can get a full 5.1 setup (subwoofer included) for a little over $900 shipped from
Ubid. I'm not sure if it would be cheaper to get all the speakers separately from Ubid, but for convenience I posted the system link. From the reviews I've read, they sound as good or better than the Klipsch Reference series. Here's a recent
review. I know there are a few satisfied users of the system on this board.
The only weak spot I could forsee with the Acoustech system is the Subwoofer. The reviewer in the above linked review says it's no slouch, but I would think one might want a little more down low. If you go with the system separately off Ubid, but without the subwoofer, the total is $720 shipped. With your $1500 budget, you could go afford a few great subwoofers, including the UFW-10 from
AV123, the Hsu VTF-2, the Hsu VTF-3 (lil over budget), the SVS PB-10ISD, the SVS PB-12ISD, or the SVS-PB-12ISD/V (again somewhat over-budget). If you wanted to spend as little as possible, you could opt for the BIC subwoofer, or a Cadence X-Sub, another great value.
As far as Axiom goes, check out this
list and see if there's anyone in your area that you can visit for a listening session. All you have to do is join the message boards and PM the user you want to visit.
Good luck with your decision!