I was actually shopping for the very same thing. Being a bit of a techie, I found exactly what I'm looking for here:
http://www.newegg.com/Product/Produc...82E16834215410
An i7 quad core with 6gb ram (expandable to 16 with 4 bays), dedicated video (the same card found on the new macbook pros), 750gb harddrive with a second harddrive bay for installing a SSD, and all the other bells and whistles for $830?!?!
Sold.