mac PCI Express - same as clones?

hey,

disclaimer - i dont have a mac at this time, but im curious about video
cards on em. if one gets a mac w/ a pci express slot, can it use the
same pci express video card hardware commonly sold to pc clone users?
(ati, nvidia, etc..)

i would imagine only mac os x drivers would have to exist for that. do
they? or is mac video hardware still a "mac edition" of the pc versions
(in which a different firmware is flashed to it)?

would be nice if it was the same hardware.. one step closer to cheaper
macs -- if i can upgrade components the way im used to on a pc clone...
(harddrives, ram, video.. about the only limitation i see is the
motherboard-cpu combo -- i dont believe thats user-upgradeable on any
mac)


thanks!
matt