I have all the bookshelf models ( I know I know, I need counsellings)
M2's are a no go with no sub, M3s are a very warm sounding speaker with nice clarity in the high end, M22s are just an amazing speaker, I love my M22s more than any other speaker in my theatre (Mabey the EP500 takes the cake, its a close call.)
For an office system, for sure the M3s are the way to go, they are less obtrusive (not nearly as tall, standing at 13.5" compared to 19") and provide the whole spectrum of sound. whens compared with the M22, the M3 does sound like it has better bass output, however, its the hump in the 100-150hz that deceives you into thinking that.
When all is said and done, I would personally get M3s for my office. We are currently using our M3s in the kitchen in my house, and I love it, they sound amazing.