looking at your scores, the gfx card is the major bottleneck. (sorry should have realised that you mentioned you had win 7 where the scores go up to 7.9, rather than the 5.9 - vista scoring that i quoted earlier)

I have a 5850 toxic 2gb in my primary system and that is a stunning card.

a 5870 should take your gfx score up to 7.5+

you will get mid to high 6's on hard disk if you upgrade to a ssd (low end 6's on high speed hd's)

have you tried downloading the latest drivers to see if that improves speed?