Machoo - I had a very similar system to you and upgraded the graphics card to an XFX 6950 2GB, recently I flashed it into a 6970 (see here
http://www.techpowerup.com/articles/...ng/vidcard/159 , but reduced the clocks back to 6950 settings just in case). Save yourself £60!
I runs CoD pretty well, with most settings on high, but I do have an old crappy monitor at 1280x1024.
Actually, the VBIOS flash didn't make much of a difference, so I suspect the rest of my machine is limiting (Q9550, 6GB RAM, Win 7-64, cheapish SSD).
The only thing I'd add is that there are some graphics artifacts (before & after VBIOS flash) that I get and others report
http://forum.1cpublishing.eu/showthread.php?t=21710 , as we're all ATI users I suspect it's a video driver problem common to all ATI cards.
56RAF_phoenix