I currently have one of the BMW Cruise hybrids that is equipped with Shimano Alivio components. The bike has been great for me, and fits very well.

Having beat on it fairly hard for 8 to 10k over 3 1/2 years a few things need to be replaced, such as the rear cassette and front deraullier (dented - don't ask).

I've gotten a little spoiled with the components on my MTB SRAM / Deore, and the CAAD SRAM Rival. As such, I am thinking about upgrading the drivetrain to something like a Deore XT or XTR. I plan on leaving the brakes, as they are good. A few questions:

- has anybody had experience with buying these groupsets new, and can recommend a good online source?
- are there any other groupsets you could recommend?
- what measurements should I look at to make sure cassettes and other components would fit? (The bike does not have braze-ons for the front cage)

I enjoy the bike, so I am not as concerned about resale value, but more functionality. Nothing wrong with the Alivio, but the better shifting and gear spacing would make the ride more enjoyable.