I am using ProAc Response 1SC's in a room slightly larger than yours (27 x 17 x 10), driven by Pass Aleph 3 and couldn't be happier. Other than ultimate loudness and deep bass, the sound is absolutely terrific and the speakers are very attractive and unobtrusive to boot. Highly recommended combination! With a room this size, the Aleph's are right about at their limit when the music gets a bit more dynamic and at moderately loud levels, I will try the Aleph 5 and it should cure that problem and I am done.
I have had the Merlin monitors, forget about them, very hi-fi sounding, the ProAcs are much better. I also like the Reynaud Trente's for about the same $$ as the Response 1SC's, the ProAcs are a bit sweeter up top and a more attractive cabinet, but the Reynauds are no slouches and the bass is a bit smoother than the little ProAcs (which unfortunately, have the classic British monitor mid-bass hump). However, you can address that midbass hump with the 1SC's in a room the size of yours very easily by simply pulling them out into the room away from the rear wall.
Whether you get Trentes, 1SC's or something similar, don't scrimp on the cables or upstream gear though! These may be (relatively) unexpensive and small loudspeakers, but the sound is absolutely first-rate.