If you live in a big metro area go and scan your local circuit city's for VR series Boston Acoustics equipment, Denon AVR-x87 series receivers, and Velo VRP or Boston XB series subs.
If you are lucky enough to find that stuff, within your $700 budget you could get a:
Denon AVR-787, 687, or 587
Pair of Boston VR2 fronts
Boston VRB center
Velo VRP-1200 or VRP-1000
All for under your budget. Add cheapie surrounds and up 'em when you have time. Boston Bravo II's are...