well the 9800 and the gts250 are both g92's, your not going to see much improvements there.
you basicly bought a 3rd generation of the 8800gts 512 (9800 was 2nd gen of the 8800gts)
amd x2 6000 ---> x3 720 is a pretty good jump.
but if you really wanted to see improvements in gaming, a gtx 260 or equivalent (or better) would have been a better choice in the gpu market.