I was just wondering how a 550 Pro-X would do against say like a '00 XC 600 without VES?

best rider will lead on the trails, drags 600 all the way

how about in teh mountains if u would put a 1" track instead of the stock .82 or .91 or whatever it is

a 1" track isnt much better then a .8! If you want deep snow capabilty you need atleast a 1.25" track, the best rider will winn an any trail race aslong as speeds are under 45~50 mph. lake race....600 non ev will leave it for dead at +40 mph! I think it would be a fun sled on tight technical trails where speeds where under 40.