If you could only use one card and had a PSU of 650 what video card you choose for the highest KHS
2nd Edition of the 7990 the one with 2x 8-pin PCI-E power (not 3x). 4096 Stream processors. Nothing beats it, it's still the king!
They were selling for as little as £400/$600 at one point just before the R9's came out.