I actually couldn't tell you at this point. All I know is that the power supply can run a 9800GT, which is what I have.
Ah well fair enough, we can always see whether or not you can swap the two... Here's what I could dig up from the nvidia site.
9800GT
Maximum Graphics Card Power (W) 105 W
Minimum Recommended System Power (W) 400 W
Supplementary Power Connectors 6-pin x2
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GTX460 (highest end model)
Maximum Graphics Card Power (W) 160 W
Minimum Recommended System Power (W) 450 W
Supplementary Power Connectors 6-pin & 6-pin
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As you can see you need to have a power supply that has AT LEAST 450W is you want to use a GTX460, that's about 50W more than your current graphics card uses. So we really need to know what kind of power supply you use. We also need to know what kind of motherboard you have, because it might be slower than the GTX460, which might cause bottlenecking.
It just came to mind that you might've purchased a standard computer from the store, if so, we can look up the specs if you can provide us the computer's model.