As I recently purchased the 8800GT graphics upgrade kit from Apple, I have my original ATI x1900xt graphics card up for sale now.
It, unlike many reports I've seen, never had overheating issues, and has never displayed any screen artifacts or other errors. It has the newest firmware, and has no issues at all. It games like a pro on both the mac and windows side, and is the original card that I purchased from Apple when I first got my Mac Pro (Fall 2006).
Included will be:
-ATI x1900xt Graphics Card ($399
At Apple Store)
-6pin-6pin Power Cable (>$12 PCI Express 6 pin to 6 pin power cable
Here)
-Zalman vf1000 ($49 high quality cooler
Here)
Whoever purchases this from me can decide whether they would like the vf1000 installed on the card, or the stock cooler, but I will include both in the sale, with all original boxes / instructions / etc.
I am asking only $175 shipped and I will accept Paypal, Cashier's Check, or Personal Check. I have heatware by the same name, and have done many successful trades, some of high value, within these forums. I can post pictures of everything if anyone would like them.
Gaming benchmarks:
http://www.barefeats.com/harper8.html
Pro Apps benchmarks:
http://www.barefeats.com/harper10.html