unless u have pci xpress then the x800 XT is alright.
....inwhich the nvidia would still beat it...
If you wait until september you can get the 128mb 6600GT its the more 'mainstream model' opposed to the 'performance model' known as the 6800...surprisingly enough though the 6600 actually has the DDR3 memory which the 128mb 6800 doesnt have. It has 8 pixel pipelines and the ATI equivelant of the 6600 (maybe the X600 I guess?) only has 4. Even with that I just read an article today that said "even if ati had those extra 4 pipelines I doubt it would help one bit" and basically concluded it with 'Dont even consider the ATI version, nvidia blows it straight out the water'
Conclusion: So it seems that in previous models ATI is better than nvidias FX series...as for the newer series, 6800's and X800's Nvidia will reign supreme...and also goes for their 6600 models.
EDIT BTW: Shoulda mentioned that the 6600 is gonna be like $199 I believe. Not a bad price at all!