The GTX 590, assuming ya can still find one, got ya 881 fps in Guru3D's game test suite for $750 or $0.85 per frame.
The 6990, assuming ya can still find one, got ya 762 fps in Guru3D's game test suite for $725or $0.95 per frame.
The 7970 gets ya 675 fps for $550 or $0.81 per frame
The 78xx series looks very interesting but since we only have buggy reference 7850 cards to look at and no one is actually going to release a reference 7850, gotta reserve judgement at this time. Should be some excitement when kepler breaks and these 78xx series get sorted out.
Twin 900Mhz 560 Ti's (w/ the beefy 7 phase VRM's) are readily available and will get ya 862 fps in Guru3D's game test suite for $420-430. That's significantly faster than any of the above, except the 590 where it comes up just 19 fps short, or about half the cost per frame @ $0.42 of any of the above.
That psu you originally mentioned is perfect. Whichever psu you decide to get make sure it is a SINGLE rail design. My craptacular psu works great but the dual rail suffers from an unbalanced load and causes system crashes if you don't balance things properly. I beleive the HX1000w has two rails and the HX850W is a single.