Just finished putting together a 2x72. I bought a variety of belts from Tru Grit, but I've heard good things about Pops as well.. Pops seems to be a little cheaper but didn't look to have the selection TruGrit had.
So far in my limited experience i'm liking my 3M cubitron ceramics for roughing and trizact gators for finishing. Also bought some cheapo AO belts in varying grits for wood handle work.