disc brake/disc wheels options

I'd like to convert my '02 Isis frame over to discs from v's. I ride
XC exclusively, mostly pretty tame trail riding with the occasional
fast downhill. I am 6'3 and weigh about 200-205 lbs. I'm scared to go
the Shimano route due to compatibility issues. What are some good
wheel and brake options and good online retailers for them? Cost is
definately a factor. I also don't want to go overboard on weight
since they will be primarily for XC.

TIA