I'd like to add another monitor (third) to my system. I currently have 2 24" Dell hooked up to a Radeon x1900, can I add another x1900? Should I just pick up a stock 7300GT? Beyond that will my system show any performance degradation? I'm using FCP, After Effects and DVD Studio Pro. Will the nvidia work with the Ati card? My specs are Mac Pro 2.66 ghz 13 gigs ram 250 gig system drive 3 x 500 gig scratch drives.