Unfortunately, you can't use SLi and run dual monitors at the same time.
Though, one 7800GTX should definitely be enough for gaming and your video editing. Here's a list of parts I would choose if I were you.DFI Ultra-DAMD 64 Athlon 3700+OCZ Performance 2GB PC3200EVGA 7800GTXOCZ 520w ModstreamSeagate Barracuda 250GB
These come to a total of $1490 CAD + shipping
Then all you need to do is add the optical drives, case, and monitors all of which should not cost more than $1500 CAD. If you want you could upgrade the CPU to an X2, but I'm not sure you would feel the performance increase for the price you pay. You may want to upgrade the stock HSF if you really want to OC with something from Zalman or Thermalright. I know you have a budget of much more than this, but the price you pay is much greater than the performance increase.
Edited by welco, 14 February 2006 - 10:39 PM.