In general, I would shy away from in-wall speakers simply because once they're installed, you can't easily move or otherwise reposition them. Plus, the ones I've heard sound uniformly inferior to comparably priced bookshelf speakers because they generally cannot play accurately in the low frequencies.
With your budget, I would also question whether or not to go with a 5.1 package. The bare minimum that I would find acceptable is the Energy Take system, and the version that's within your price range I'm not sure if it includes the subwoofer.
I would suggest that you build your system gradually rather than buying the entire speaker package at the same time. With a $750 budget, you can get a pair of decent on-wall speakers, but not much more. A good subwoofer alone will run you at least $400. (With bookshelf speakers, you can probably buy three, but the good ones will generally not wall-mount very easily and won't sound their best with that kind of close placement.)
The on-wall speakers in your price range come from Klipsch, Boston Acoustics, Definitive Technology, B&W, Paradigm, and Vienna Acoustics. Give those a listen, and be patient. You can always build the system as funds become available. In the end, you'll end up with a much higher performance system that's better suited to long-term enjoyment.
I have the Boston Acoustics 130 micros with the Boston VRC, center channel, it's a little pricyand the Velodyn spl800 sub and it sounds great. Check out their website I paid $250 each for the speakers and $400 for the Center Channel you might find a better price online I went with the 130's because of the frequency response 80 (which is the suggested THX crossover setting)