Try and avoid buying buy brand name alone. An owner of an Antec SG-850 for example might say that his PSU is as close as you can get to an affordable "State of the Art" PSU (assuming you agree that $250 is affordable) and he's be right ..... but buying an Antec Basiq or Neo series can get you nothing above a no-name brand.
I think it's safe to say that the 570 and 560 will draw less power than the 470 (227 watts) and 460-1GB (177 watts).
http://www.antec.outervision.com/PSUEngine
You could get away with less but the sweet spot for single GFX card PSU's is 650 watts. Extra power availability doesn't burn electricity and, if ya look at the curves, efficiency peaks at 50% load. For comparison purposes , the list below contains performance ratings (10 scale) at jonnyguru.com / prices as per newegg on 02/26/2010 (I'll update over holidays) and ones w/ double asterisk (**) made it onto silentpcreview.com's Editor's Choice List:
Note: Just because you see a brand name on this list, never make the assumption that their other lines are of matching quality. Silverstone for example has other models w/ 6.0 and 7.0 ratings.
Antec Signature 650W (10.0) OOS **
Seasonic X-650 650W (10.0) $160 **
Silverstone Olympia OP650 (10.0) NFS
Thermaltake Toughpower QFan 650W (9.5) NLA
Antec Earthwatts EA650 650W (9.0) $75
Antec True Power Trio 650W (7.5) NLA
XFX XPS 650W XXX Edition Power Supply (7.0) NFS
Antec NeoPower Blue 650W (6.5) NLA
BFG BFGR650PSU 650W (6.0) NLA
NorthQ Black Magic Flex 650W PSU (5.0) NFS
NFS - Not For Sale / NLA = No Longer Available / OOS - Out of Stock
Now if ya thinking you might SLI that rig someday, best to buy the capability now. An 850 will handle twin 570's since it easily handles twin 470's. I built 3 SLI rigs with the 470 this week and the fans on the CP-850 hardly spin up under load. For comparison purposes, again , the list below contains performance ratings (10 scale) at jonnyguru.com / prices as per newegg on 02/21/2010 and. again, 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) **
XFX 850W Black Edition 10.0 ($185)
Corsair HX850 850W - 10.0 ($180)
Antec TruePower Quattro (TPQ-850) - 9.5 ($150)
Corsair TX850 - 9.5 ($140)
Seasonic M12D 850W - 9.5 (NLA) **
NorthQ Giant Connector 850W - 9.5 (NFS)
Etasis ET850 - 9.5 (NLA)
Silverstone Zeus ST85ZF - 9.5 (NLA)
Enermax Revolution 85+ 850W - 9.0 ($250)
Thrmaltake Toughpower XT 850W - 8.5 ($216)
OCZ Z Series 850W - 8.5 ($200)
NorthQ Black Magic Flex 850W - 8.0 (NFS)
Coolmax CTG-850 - 8.0 (NFS)
SilverStone Decathlon DA850 - 7.5 ($230)
Enermax Galaxy DXX 850W EGX850EWL - 7.5 (NFS)
SilverStone Strider ST85F - 7.0
Silverstone Element ST85EF 850W - 6.0
If ya have a compatible Antec CPX form factor case, (P183, P193, 1200, DF series), the CP-850 is a no brainer. It matches the top of the line units from Corsair (HX Series) and Antec (SG-Series) in performance, is about 1/2 to 2/3 the price of the competition at 850 and is quieter than they are. If I was OC'ing and / or using SLI, I would limit myself to these choices.
If only using one card and not going too crazy w/ the OC'ing, I'd get the Corsair TX series or the Antec TP or EA series. I have seen some good reviews of the Cooler Master Real Power Pro (Different animal than the less well received "Silent Pro" series). Avoid the GX series as its performance rating was a 6.0 any jonny's. The UCP series and "Silent Pro
M" series has some good reviews.