Upgrading GC in Dimension 9200

Hello,

I have a Dell Dimension 9200 with the following spec:
Q6600
4GB RAM
2x320Gb HDD
Vista Home Premium (32-bit)
Nvidia 8800GTX (768MB)

I'm pretty sure the graphics card has died, can anyone recommend a decent card to get me a couple more years out of the PC, ideally without upgrading the PSU (original 375W)?

I was looking at the Geforce GTX 460, about £120 and uses slightly less power (150 vs 155 Watts according to wikipedia) than the existing card.

This should give me a decent performance boost, but is this pushing it too far? Would it be wiser to go for something more lower power, or go all out and upgrade the PSU as well?

I'm a bit put off by an article saying you have to take off the heat sink assembly to change PSU in these machines, sounds like a lot of hassle.

Cheers in advance.