I have a Gigabyte 9600 PRO in a machine rotting in the attic, but it works perfectly in a 4x and 2x slot. The PowerColor is probably the same. Same reference design. Ask around for more opinions, but you won't find many, the card is extremely old.
Does your 9600 Pro also have the two cuts on the AGP connector like mine? Remember, AGP 2X is 3.3V only. And from what I've read on ATI's website 9600 series Radeons were only designed to run a 4x or 8x (1.5v).
I'm a bit torn on this one. On the one hand, all signs point to the fact that I'll probably fry the card if I insert it into a 3.3v slot.
On the other hand, why is the card keyed for 3.3v if it's not compatible?