A 9500GT should be just fine. A Radeon 4670 or a GT240 would certainly be better and should work assuming that your PSU was decent enough and that the rest of your system doesn't draw out too much power. The 4670 uses around 65W peak, but that's in stress testing and not likely to happen in games. The GT240 uses less power at its peak, like 51W, but on average it's much closer in power usage to the 9500GT. The 9500GT only uses like 44W peak, with furmark, but on average is lower and thus should be fine with just about any PSU. The GT240 is the fastest of the three, but of course the Radeon 4670 is a bit cheaper.
Hmm... looking it up it seems that the PSU is only 300W and some people are having trouble using a Radeon 4670 with that system. Of course they could simply have not properly removed the older drivers, but in some cases it looks like the PSU is the culprit, while others say it runs just fine.
I'd go with the GT240, but if that's out of your price range then go with the 9500GT and you should be fine. Just make sure to properly remove the Radeon drivers.