But for the money, the 4650 should do great as well.
Oh, keep in mind on the 9600gt, don't know about the power requirements on the low profiles. I know the normal ones do require a power connector. So keep that in mind. If your power supply seems too weak, then definitely the 4650 as that is one it's biggest advantages.
Unfortunately shadow you skipped the low profile restriction. The low profile ready cards im not sure how you get them to turn into low profile cards, the 4650 was the strongest low power card i could find and it doesnt require extra power.