Just built a solid pc from scratch for my in laws - evga x58 sli3 mobo (w usb 3 - why not), i7 920, 4 gig ram, 1 tb hd, cheap pci express card, 600 watt ps, thermal takev4, dvdr/w. And that was bought at a store (microcenter), including tax, for $620. If you just tacked on a good video card, add $300 (and subtract $20 for the low end video card I bought them) and your total is $900 for a gaming rig that can play pretty much anything out there.
Of course, then you still have to pick up an os, to be fair, so depending on your options, you can get win7 for $30-$100. Total price for a decent gaming rig - $930-$1000.
Drop the liquid cooling, get the Cooler Master 212 + Artic Silver 5.
Agreed - you can get that for like $25 on amazon now with free shipping.
And honestly, I tend to think dual video cards are a bit of a waste - eg price is not worth the performance. I'm hitting at least 60fps on 1 single 5850 with anything I can throw at it.
If you really want to be thrifty and actually want to build one yourself, then I'd suggest checking out www.slickdeals.net. They have a thread that regularly updates current pc parts and finds the best deals going on. I think I got my previous cpu (i920) for $100 back when the best online price was $200.