Well I would recommend the 7900GTX over the x1900xtx. They are about the same price.
For $490:
x 1900xtx:
650MHz core
1500MHz memory
16 pipelines
256-bit
512MB GDDR3
7900GTX:
665MHz core
1630MHz memory
24 pipelines
256-bit
512MB GDDR3
Have a looksee here:
http://techreport.com/onearticle.x/9780
http://www.theinquirer.net/?article=30856
It seems that they are pretty much even in performance, but the x1900xtx is so loud, I would never buy it over the 7900gtx
For $490:
x 1900xtx:
650MHz core
1500MHz memory
16 pipelines
256-bit
512MB GDDR3
7900GTX:
665MHz core
1630MHz memory
24 pipelines
256-bit
512MB GDDR3
Have a looksee here:
http://techreport.com/onearticle.x/9780
http://www.theinquirer.net/?article=30856
It seems that they are pretty much even in performance, but the x1900xtx is so loud, I would never buy it over the 7900gtx