GeForce FX 5500:
I can't for the life of me find any stats on the 9600se pci. I think that both card perform about the same, however, so you shouldn't be disappointed either way.
go for the radeon, it has better shaders. in HL2 you could run it in DX9 or get the FX and run it DX8.1. i've seen a 9600SE in action, and all i know is that it can play city of hero's maxed no problem
The SE is less powerful. Get the 9600 Pro or XT if you are looking into that line of cards. The SE is a crippled version of the 9600 Pro. Definately don't go with an SE card if you are going higher end.