I think the Studio monitors would be a good fit as well, so long as you don't mind the higher bass role off. If you were to add a single 12" sealed servo sub, he'd have it all.
Another thing worth considering, monitors on stands take up as much real estate as a floor stander, or very close to it. Not sure how big the room is but the NX Otica's with a bit of room gain play down pretty decently, as the room gets larger, the role off happens earlier/higher. In my 18x12 room, the Otica's played down to the 40 hz range , with a little dsp, I was able to get them to play almost to 30 fairly flat .
As you've mentioned, you do have to keep that 3" minimum in mind for the full OB speakers....
With regards to the MTM version, you'll need subs for sure with them
jay