I can't vouch for vid editing, but I've switched off XP and am running just Fedora 7 now.
For me, I can game, do php/sql/apache web work in a test lab setup, plus I can view and paly 99.9% of videos, music etc.. all on an open source OS that didn't cost a dime to get, and took just a few hours to really get tuned up to where I wanted it.
I don't know if it would be practical for you though, sounds like you want to get a pretty high end box. Good luck with that.. I hate computers, so I can't in good conscience tell you to spend your money on one
