+1 on an off the shelf Dell.
I bought a Dell in early 2011 to replace my dying xp machine. Mine has the Intel Core i7-2600 (Sandy Bridge) CPU @3.4GHz, 8GB RAM, 64bit OS, multiple internal & external hard drives. It's great. Super stable, with enough power to do what I need it to do.
One thing: Make sure your i7 is a Sandy Bridge.