It'll all work together great. The PSU you picked has the exact same dimensions as the one HP put in there. Looks like you're good to go. Although you could easily get away with a 380W or 430W PSU.
I was going to go with a 430W PSU, but couldn't find one that was certified and as awesome as this one. This is a great deal, unless you can find a 380W or 430W PSU for me, that would be great. :P