i cant believe you've settled for the 9500GT for so long (given your system specs)

, im trying to work out why the cards have a different bandwidth..??, they're both running 1024mb of DDR2....the RAM on the 9500 must be clocked higher than the 9600, (or its a misprint)
''IMO'' forget the 9600GT, i'd look at the GTS250 or the GTX260 (budget & PSU permitting), the cards ive listed are pretty cheap now, the release of GT300 will see the current prices drop even further...
your Q6600 is SCREAMING for a decent GPU... dont dissapoint her.......lol