Video Rendering for iMAC

Just wondering if there is video rendering hardware available for the
iMac from avid or matrox, or are they limited to the higher end
desktops that can take internal cards.

Also, anyone know of any video cleaning software for mac? I have some
old footage that has a lot of video noise. I have used virtual dub on
the pc, but would rather use mac if there is a program.


Thanks
Mark