Here are a few that you should consider for a PSU.
PSU - $60 shipped - $5 MIR = $55
FSP Group (Fortron Source) AX500-PN ATX2.2 500W Power Supply 110-120/ 220-240V UL, CSA, VDE, NEMKO, TUV, CE, CB, FCC - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E16817104037
PSU - $60 shipped Hard to beat at this price
Antec earthwatts EA430 ATX12V v2.0 430W Power Supply 100 - 240 V UL, CUL, FCC, TUV, CE, CB, C-tick, CCC – Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371006
PSU - $100 shipped - $45 MIR = $55, can’t beat for this price
Antec NeoPower NeoHE 550 ATX12V 550W Power Supply 100 - 240 V UL, CUL, TUV, CE, FCC, CCC, CB, C-tick – Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E16817103941
Any of these will work for almost any video card. The 550w Antec would be the best buy, but you'll have to wait for the $45 MIR (if you trust MIR's).
If I had to choose between the x2600 or 8600gt, I would get teh x2600xt. But if I was spending correctly, I would get the x1950pro, it'll play games much better than any of the x2600's or the 8600 gt's.