The 9600 pro is easily the best choice out of those.
The ultra 5600 pro revision 2 is a good card also, and superior IMHO even for the extra $50 or whatever street price differences come to.
Remember if you are switching brands in a system from ATI/NV already, you will have to reformat!
This is one of my small reasons I dont want to switch to ATI atm. Esp with an option such as the 5600ultra rev2.
I used to format every 6months but find it annoying as heck anymore.
If you are limiting your choices to strictly those cards, and you have nvidia right now, i'd still recommend the 9600pro even with a format.
otherwise take a good look at the ultra rev2.
Good luck!
Athlon 1700+, Epox 8RDA (NForce2), Maxtor Diamondmax Plus 9 80GB 8MB cache, 2x256mb Crucial PC2100 in Dual DDR, Geforce 3, Audigy, Z560s, MX500