Absolutely the GTX460. It's the best bang for buck out there... just make sure you opt foro the 1gb version. Not only does it have extra memory, but it has several other increases the normal 460 doesnt.
Plus its always a good idea to run Geforce cards with intel processors to minimized driver issues in the future.
Unfortunately, you won't be running two of them in SLI with that power supply. Under full load they draw nearly 300watts
Wow, loads of input. Thanks for your help guys. I found the 1gb version for only 220$ at newegg.ca so I think I'll go for that. As for SLI it, a single card should be just fine for a good long while so I'll sort that out when the time comes.