^+1 on the RAM issue.
Wouldn't say the 750Ti is exactly slow, though: It's capable of running med/high settings at 1080 res, even in demanding games and in my opinion a pretty perfect match for a stock speed Q6600/1080 monitor.
Depending on how much eye candy you want either the GTX750 (lower end) or GTX750Ti (upper end) would be a big upgrade, they're fairly compact, should be quiet and draw as much, or less power than the 9500GT.
Bear in mind, both those cards are very new and are very energy efficient so they don't usually need an external 6 pin PCI-E power lead from the power supply to run, but check any 750Ti you have in mind, just to make sure.