These guys are diverse in their work which includes tree removal and stump removal / grinding. They say its how they can keep their prices lower than others, which seems to be true. I would recomend asking them anything you need; and if you were in CO then having them come out.

If the stump is larger than about 18" from one side to the another, the rental grinders may be to small. Another thing to keep in mind however, is if using a real stump grinder (the big ones) they may need, like these guys did, 7' of access to get in there (such as if the stump was in a back yard). Here is their info - Colorado Creations - theccllc.com / info@theccllc.com