Let me explain my current setup. I replaced my PC with my new shiny MacPro. I made a seperate thread on this, and wont post the details. I am keeping my custom display setup and wanted Quad LCD's to work on the MacPro, but wanted a fast video card setup to play WoW. The NV7300 is a joke compared to any real video card, so I knew I wanted to get either an ATI X1900XT + NV7300 or two ATI X1900XT's in the system at once. Here is a picture of how it looked on my PC. Here are my current findings: ATI X1900XT (slot 1- 16x) + NV7300GT (slot 4 - 8x) - FAILURE Well, it does and doesn't work. It DOES boot and work for all normal work. But, there are a few funky things going on. The OpenGL system must go into a "compatibility" mode because WoW performance drops by ~30% on the ATI vs when it's the only card in the system. Also, Aperture crashes if its launched on the ATI screens vs the NV screens. I read up and found out that Aperture actually uses the GPU to generate previews for each shot. The app works fine if you leave it on a screen with the NV7300, but as soon as you move it to an ATI screen, it crashes. iMovie Quartz effects also do not work reliably on either screen. ATI X1900XT (slot 1 - 8x) + ATI X1900XT (slot 2 - 8x) - SUCCESS Kinda... I didn't want to go this route because of the cost, but after spending $6700 so far on the setup, what's another $400? Everything works fine in this setup. Aperture, iMovie, FCEHD all work perfectly. WoW runs great on the screen's with the Primary slot 1 card. If you move WoW to a screen on the slot 2 card, it runs horribly. This is probably a WoW thing. But I am having random lockups on various things. At first, I couldn't put my finger on it. But I am able to reproduce one lock 100% of the time. If I move my SlingPlayer window from a card 1 screen to a card 2 screen or visa versa, the screen would freeze, almost like both GPU's locked up. The mouse cursor still moved, and I could SSH and do all console activity on the box. It would take a "sudo reboot" and shut down properly. Parallels also would cause a random lock even if its just sitting on a single screen. I could not convince myself that it wasn't a HW issue with card 2, so I decided to swap card positions (moved slot 1 to slot 2, and slot 2 to slot 1) and see if the symptoms changed. Now when I moved the SlingPlayer from screens of both cards, the entire MacPro would simply reboot; No warning, nothing... Boom Reboot. I repeated this many times to make sure the crash was repeatable. It was to a certain degree. It would randomly crash and reboot or do a GPU lockup like before. I put my original X1900XT back in, removed my new one, and issued an RMA to Apple. I am going to swap out card 2 to remove doubts about bad HW. PS. Bootcamp won't even POST with both ATI cards in the machine. By POST, I mean, if i hold [ option ] and pick my bootcamp partition, it just hangs. I have to remove ATI card 2 before it can boot up. What's up with that? RANT Why does Apple not give more video card options? Why can they not give me a Killer 7900 or 8800 Nvidia card to mix with my puny 7300GT so I can have good performance on my primary screen? Why does Apple not give an option for a crappy ATI card to compliment the X1900XT so I don't have to waste $400 on a card that will never be used to its fullest extent? Is multi-screen (3+) that uncommon on professional computers? It seems the only way one can do this in a supported fashion is to put a ton of crappy 7300GT's in the mac. I've been doing this on my old XP box for YEARS without any issues whatsoever. So far I'm pretty pissed about this whole experience. I will report my results when I get the RMA'd card on Friday.