You decide:
Guru3D uses the following games in their test suite, COD-MW, Bad Company 2, Dirt 2, Far Cry 2, Metro 2033, Dawn of Discovery, Crysis Warhead. Total fps (summing fps in each game @ 1920 x 1200) for the various options in parenthesis (single card / SL or CF) are tabulated below along with their cost in dollars per frame single card - CF or SLI:
For example, blow it reads that the 570 gives ya 524 fps in single card config at a cost of $0.61 per frame and 873 fps at $0.73 per frame
$ 200.00 560 Ti (455/792) $ 0.44 - $ 0.51
$ 215.00 560 Ti - 900 Mhz (495/862) $ 0.43 - $ 0.50
$ 270.00 560-448 (501/835) $ 0.54 - $ 0.65
$ 320.00 570 (524/873) $ 0.61 - $ 0.73
$ 450.00 580 (616/953) $ 0.73 - $ 0.94
$ 480.00 7950 (603/NG) $ 0.80 - ERR
$ 560.00 7970 (675/NG) $ 0.83 - ERR
Since ya mentioned $400
.....
Two of the bolded cards in SLI (862 fps) have a cost per frame of $0.50 ($430) .... well below the 570 and 580, not to mention 7950 and 7970. And, with the over size coolers and beefed up VRM's on the PCB, they OC like a beast (as high as 30+% over reference)
http://www.pureoverclock.com/review.php?id=1201&page=17
The two 560s will give ya 862 fps .... 40% more than the more expensive single 580 !!! That might even be worth sleeping on the couch cause ya won't be sleepin', you'll be playing till all hours
If ya get a 570, make sure that ya check the number of VRM phases on the PCB ... ya gonna want at least 8. Asus, Gigabyte, Gainward all have 8 phase designs, MSI has 6,8 and 10
http://www.overclock.net/t/929152/have-you-killed-a-570-no-recent-deaths-buy-some-570s/550
However, w/ Kepler arriving in 6 days, ya may wanna see what happens first. And don't count the 78xx series outta the picture..... we've seen the paper launch of the reference 78xx series but not a single manufacturer is releasing a reference board.....that tells me to expect more than we have seen so far.