MATROX have kick-ass multi-monitor supports/software. You can get a triple display card.
<A HREF="http://www.matrox.com/mga/workstation/video/home.cfm" target="_new">http://www.matrox.com/mga/workstation/video/home.cfm</A>
MATROX will gives you all you need with Video Editing.
By the way, if you mainly do video editing, you should consider Power MAC G5. My friend have a dual G5 (he do video editing for living) and he really loves the performance. He can render in realtime at broadcast quality most of the time.
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Lookin' to fill that <font color=blue>GOD</font color=blue> shape hole!