The answer will depend on power supply size, what case ya got and resolution ya play at.
But facing the same question, two of my son's friends that I did builds for last week went with twin factory OC'd 470's which are cheaper than the 580 and certainly outperform it by a significant margin
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130549
I torture tested the rig for 48 hours and running OCCT GPU test was not able to get GPU temps over 82C and that was with all case fans set to the lowest of the three available settings. For the 470's a good 850 watt PSU is needed:
For comparison purposes , the list below contains performance ratings (10 scale) at jonnyguru.com / prices as per newegg on 02/21/2010 and ones w/ double asterisks (**) made it onto silentpcreview.com's Editor's Choice List meaning they excelled at both electronic and acoustic performance:
Antec SG-850 - 10.0 ($220) **
Antec CP-850 - 10.0 ($110) ** (requires compatible Antec case)
XFX 850W Black Edition 10.0 ($185)
Corsair HX850 850W - 10.0 ($180)