Should I get an EVGA GTX 465 Super-Clocked or a XFX Radeon HD 6850?

You should actually consider purchasing a 460 card instead of a 465, since the 460 is much faster and the 465 are almost out of market and don't have much user base in case you run into problems. However, if it must be absolutely be between those two, I would rather choose the 6850 because its faster and has a large user base on the card. Also, a 6850 scales alot better when you crossfire.