I'll have to take a look at XtremeSystems.
I didn't disable anything, all I tried was putting the card in different slots. I don't recall seeing a way to disable the onboard storage controllers, so I will have to look into that. Since the 2604 works, would there be any reason to believe a RR 3620 wouldn't work? I looked at the compatibility lists for both and they listed a similar p67 motherboard made by Gigabyte.