I'm going to have to say that it's a waste of money. Just use two video cards, that way in the future you'll have an easier upgrade path. For instance buy a high end AGP card (ATI 9800 Pro or so) and then buy a lower end PCI card with DVI. This way when the your 9800 pro can't cut it any more you can just upgrade that card and leave the PCI. Should cost you much less in the long run and short run
The xeon processors are definitely overkill. A dual system would be cool if you're going to be doing a lot of recording and work at the same time. Otherwise I don't really see a benefit. Stick to the plain P4's, it'll save you a lot of cash.