I don't quite agree with your lists. I would put 6800GT, X800XL, X800XT, X800XTPE, X850XT, X850XTPE, 7800GT, 7800GTX in the first category and 6600GT, 6800, X800, X800 pro in the second list. There is no X850 and X850 Pros are extremely rare (and bad cards for the price anyway). The 6800 ultra is not worth considering; it always was a ripoff given how close the GT was to it and is even more so now since its price has not fallen much after a year.
I'm not sure if even the high end cards from last generation are going to cut it at decent resolutions though, say a year from now. My overclocked 6800 GT struggles on games like FEAR even at 1024x768. Don't know if it's just this game or a sign of things to come. UT2007 will be a good indicator of future performance. Also, most modern games are limited to 1280x960, or if 4XAA or HDR is used, then 1024x768. Older games work great though; FSO is liquid smooth at 2048x1536.
I would have gotten a 7800GTX but it would mean a new motherboard purchase just for PCIE support, which seems to be a waste at this point given that the M2 socket is coming early next year. I will just wait it out, maybe skip this generation or see what the R520 (which will be in AGP) has to offer if it ever comes out.