can I use any brand x1900XT in the mac pro. For instance, can I buy a PowerColor x1900XT pci-e and stick it in there? Or does the one available through ATI/Apple have a specific bios. Only reason I ask is because Apple messed up my order and I had to cancel it, wait 5 days for pre-verification to drop off (doing this now....) and then re-order. So I will be mac-proless for 3 more weeks. I was going to go to the apple store and upgrade to the x1900 untill I learned they charge $400 as opposed to $250.