thanks 01die i had looked at this gpu and a 550ti,a lot of reviewers have complained of different power supplies squealing [noisy] i am newby just wanna get it right,and also if it says 600 watts does that mean only if it needs the power that it uses it, once again thanks
Corsair is a good brand, but I recommend 500 watts minimum. The rosewill I recommend has around 50 amps on the 12v rail, and good newegg reviews. If you want modular, you'll need to spend around $90 or more for a decent brand with 50 amps on the 12v rail, so the rosewill isn't a bad choice. If you can travel to a microcenter, you should be able to get a motherboard combo with the motherboard almost free after discounts. Talk to a store manager if the salesperson doesn't know what discounts are available.
hd 6850 and the gtx 560ti are both same different in price, but performance wise are very close, just get the 6850 and for the psu, get seasonic psu, a good seasonic 520e 80plus bronze is gonna be your best bet, but if you really want good psu go grab the seasonic x-1250w 80plus gold (assuming they still have that 15% off) as it would be cheaper than the 850w 80plus gold of seasonic