Even with mine at 2.5 ghz there are inherant slowdowns.
There's going to be slowdowns regardless of your CPU.
Regardless, an X1900 XT isn't going to be crippled by a 3200+.
From what i can tell, all of those CPU benchmarks at Anand were 1024x768... Who uses an X1900 XT at 1024x768?
One title in 100 might perform like Oblivion and show a notable difference, but even that was limited to about 10 fps for 800 Mhz of CPU clockspeed.
While a faster CPU might be better, it's not like an e6800 would provide you with a totally different gaming experience... my two cents, anyway.