i dont actually know..i guess its the one that came with it? slots 3-4 slots are empty, slot 1 has a double wide installed..this is where it would go right?
Your monitor is not likely to go the full HD resolution of 1920x1080, but the picture will be scaled down. A flatscreen TV will probably give better picture quality.
I thought general video playing was handled by the cpu in OS X? Maybe with the exception of .h264...
If that is the case your MP shouldn't have a problem with 1080p, my old Mini with a 1.66Ghz Core Duo could almost do it, and it was solid with 720p MKV's
I browsed the EVGA website to check the requirements for the GTX 285 and you need an early 2008 mac pro at a minimum. I would imagine the same may be true for future offerings from both ATI and Nvidia. That's something to consider as well if you plan on gaming on OSX.
It does make me wonder however, how seamless the process is to install Win7 on an early 2008 and use a PC Nvidia/ATI card.