I have an original, base model launch 2006 Mac Pro, which I've upgraded everything except the Video card for. I've seen so many threads and things for sale, but I'm losing track of what is compatible with my machine since everyone else is on a 2008+ model. Can someone recommend a card that will handle modern Steam games (aka. Portal 2) at 1920x1200? P.S. I'd prefer to not flash anything (as I don't have Bootcamp available, unless I could do it from a USB Drive) and I don't want to lose my Bootscreen.