You can use almost any standard ATX psu, you just don't want to exceed the length of the original by to much.
Look for something like the Antec EA430 , they have a 500 watt unit but it's overkill for anything you could add to the 5150.
I have the same computer with the same question. I have a Sparkle GeForce NVIDIA physX technology 9800GT 1g PCIE video card that requires 400watt with required 12v 26a. Can I get a PSU that has dual 12v? For example, 12V1@18a, 12V2@15a? Will that be enough or does the 26a need to be on a single rail?