The GTX 460 requires at least a 450W PSU with at least a 24Amp 12V rail.
Im not sure about the PSU you curently have as I've never heard of that brand before. Couldn't say if its a good or bad one quite honestly.
But bear in mind, the advertised wattge doesn't really mean that much. The 12V rail amperage and effeciency is the most important.
To find out how much power the 12V supplies on the current one, look at the sticker on the side of the PSU and see what it says for the 12V voltages.
If its lacking, Something like a 450W 32Amp Corsair would do nicely for your system.
However, something like a 500 or 550W would give more headroom, allowing for additional future upgrades.
Corsair and Antec are very good choices, and are usualluy at least 80% effecient or better.
If your current one meets the Min. requirements you need, yet is only 70% effecient for example ..
Replacing the Power Supply for a higher quality, more effecient one isn't a bad idea.
Not only will it run cooler, but use less electricity from the wall to do more.