Re:
If you aren't too anal about things, chains and chain rings are interchangeable with anything in the correct BCD. Cassettes are a challenge, but out there and it's not too hard to build up a stash of spares (I've got a fair few). I think the quality and finish of xc pro is better than m900. As some have mentioned, the thumbies are great and you can get some that allow 7 or 8 speed indexing by moving a dial at the lever. Not sure if it means you can get away with 9 speed with a bit of extra push, never tried. It's a shame the rear hub since is specific for suntour cassettes as the hubs are excellent with the grease guard system, as are BBS and headsets. I wonder if there is a way to make a normal cassette fit somehow? Simple solution is to run a non suntour rear hub or both if non matching kit bothers you (it does me), as I believe shifting still works on non suntour cassettes.