This is just my opinion, but...

I'd highly suggest you stay very far away from GPU mining with video cards. I bought 9 MSI 7950's for $330 a piece a few months ago. Those suckers heat up a room FAST, and eat lots of power. I'd get a few older, used computers with lots of pci slots, and throw a few 4 port PCI USB cards into them, then buy a bunch of USB Block Erupters. Put 10 port usb hubs in each of the usb ports on the computer, and fill those USB hubs up with the USB Block Erupters. I choose USB Block Erupters cause they're actually shipping, and I got mine fast. I'm replacing all of my video cards with USB Block Erupters, as people buy them from me off of craigs list. They're cheaper, produce less heat, and you'll get an ROI faster. 2 USB Block Erupters @ 1.05 BTC each (about $160) gives you nearly the same hashing power as a $320 7950 video card.

Hope that helps.