I've found a handful of threads and comments where people had this trouble with a DA or a QS and were unable to get around it. It seems it's more common that it does work, but maybe I'm just one of the unlucky ones. Every other upgrade I've attempted to do to this machine has resulted it in it not booting properly, so at least it's consistent. My goal was to get a GPU that performed better, and also supported Core Image for Leopard, but the 9600 seemed to be the only reasonably priced option.
Anyway, I should have mentioned before that I forgot to unplug the computer when I installed it initially, and when I plugged the card into the logic board, the machine started before the card was fully seated, so I don't know if I could have fried the card. I know the logic board is fine, because the original card still works. I played around with it a bit more last night, thinking maybe the tape on the pins was getting dislodged, so I tried booting without pin 3 or pin 11 taped. Without pin 3 taped, it wouldn't do anything, as expected, and without pin 11 taped, it would chime but wouldn't go any further than that. No power to the peripherals when it won't fully boot (coincidentally the SiI3112 SATA card I just tried to put in this week behaved the same way, though I think I found the fix for that). With pin 11 taped, it boots most of the time, but sometimes it hangs after the chime and requires a reboot to boot OS X, so that leads me to believe that the logic board just doesn't like the 9600, or that the card is dead.