True though this one...
...is quite a stretch, TBH.
AFAIR DX7 vs DX9 were really different - I remember how surprised I was when I first 'geared' down, just out of curiosity... BTW I was playing CoD2 on my former 4400+ with x1900 in 1920x1200 'cause that high you don't need more than 2xAA. 
I'm sure you've probably addressed this in another thread, but why DX7 for CoD2?
Performance is about three times faster but the hit in IQ is minimal. Then with the extra performance I can crank the settings and improve the overall IQ.
Under DX9 I'd probably need to be running under low resolutions like 1152x864 or 1280x960 to keep those AA and performance levels and even lower to keep 8xS.
...is quite a stretch, TBH.