If i had that much money id buy this.
Umart Computer Notebook&PC Parts - Umart Online® Your one stop Computer Shop for computer parts,notebook and new system
Go to that link the go to Desktop Computers on the left -> Computer Package -> Umart weekly computer special series -> Intel core i5 3570k Turbo pack.
It's a custom built really nice PC.
It's an excellent PC for its price range the only thing i would change is the processor and get an i7.
P.S If you change your mind and try to build one i recomend buying a GTX 610+ as the ATi in the $800 is worser than a 550 lol. You can probably get your hands on a GTX 610 for around 100-200 on ebay.