Yeah, the next gen cards from ATI aren't going to be anything to shout about due to them being around the performance of the already released 7800GTX. If you want to wait for the best next gen card, wait for either the nVidia G70 Ultra, or the G72. Unfortunately, they are due for release sometime late next year.
So my advice would be to either go with the 6800 GT, or if you want to stick with a graphics card for quite a while, get the 7800GTX. Depends how much you are willing to spend!
<center>Athlon 64 X2 Dual Core 4200+ 512KB l Gigabyte GA-K8N-XP Sli Motherboard l XFX GeForce 7800 GTX 256Mb (450/1250) l OCZ 2Gb (2 x 1Gb) Dual Channel Platinum Series DDR400 l Maxtor Diamondmax 250Gb SATA 7200rpm 16Mb Cache l Enermax 600W Noisetaker l NEC ND-3540A Black Dual Layer DVD+/-RW l Sony 3.5\" FDD l Black Coolermaster Aerogate 2 Fan Controller l Extreme Gaming Spider Case l Viewsonic VX924 19\" TFT 4ms Response Time l Logitek MX518 l Saitek Eclipse l Windows XP Professional Service Pack 2</center>