IME/IMO...it's overkill for rehearsal, and in small gig situations...
- For rehearsal, I use a 1x15...it's low to the ground, so I can use it as a seat too...lol
- For small club gigs, I use mostly a 2x12 (which is really more than I need also)
- For larger clubs/venues/festivals, I will use a 6x10, or a 4x10, or a combination of other stuff...
Why would you need to move that much air in either of those situations? Rehearsal is for working on new material, solidifying bumpy areas in songs, changing/correcting parts, etc...Sometimes you need to be able to communicate while working on those parts/songs, and again IMO, volume should stay at a level to allow this communication.
Secondly, real estate in a small club situation is typically a big problem...lugging a 6x10 into a small club can also irritate club managers and owners (not that they are my friends or anything...but they do write the checks)...and cause setup problems with other band members.
I'm sure a lot of people will disagree, and that's cool...but I have a 6x10 that I only bring out once in a while when we do large venues or festival gigs...never to small clubs or rehearsal