MAC Pro Graphics Card Questions??? Please Help

Hello,

I am new to this group and am trying to upgrade my Mac Pro. I
have a few questions on the upgrading of the graphics card. I know
that the Apple website sells upgrades, however, I am wondering if
there are any other cards that will work on the MAC Pro. I currently
have the basic Nivida card and was weighing out the differences
between the two other cards Apple offers the high end Nvidia and the
ATI. Is one really better than the other??? I have read several
posts on the ATI card overheating....is this an issue with the Nvidia
card??? I have also read a little about flashing cards. I think I
understand the process, however, where do you get the rom images to
flash....and what cards can be flashed. I know that the PC version of
the Nvidia high end card is much cheaper than the MAc version. I was
wondering if anyone has been able to flash the PC version over to
Mac. Any help would be appreciated. You can email me directly with
any help or answers to "rabus@insightbb.com"

Thanks in advance,

Jon