You really cannot go wrong with the M30's. There are many, many speakers out there and a large number of monitors that would "fit" in a small space like yours. However, there is only one speaker that I can recommend without reservation given the parameters you have shared--the M30. ATC makes some nice speakers--the larger active monitors are capable of producing an extremely convincing portrait of large orchestral music and can rock like crazy. However, IMHO, the SCM 40 is 1) going to be too large and move too much air for that space (I wouldn't even recommend the smaller SCM 35 in your application) and 2) the Harbeth is simply a better speaker--regardless of the room limitations. The ATC will sound like hifi in comparison to the Harbeth which will sound real and alive. The Harbeth is also less fussy about what you put in front of them and where you place them. If the choice is between these two speakers, given your room, system and taste in music, it is a no brainer. Now, are there some other small monitors that you might like better? Perhaps--I can't account for your taste. But your biggest issue is the room. I've set up in a lot of small spaces and the one thing that I can recommend to you is that you NOT try and go too deep. Your room cannot sustain frequencies below a certain level--say 45hz--and if you overload the room with bass from a larger speaker (or your subwoofer) you are not going to be happy in the long run.