I know this response is too late, but this should be a popular topic so I'd like to give my opinion to help others.
I listened to B&W CM1s, PSB Imagine B, PSB B6, Revel Concerta M12, Paradigm Studio 20s, and Kef Q300.
General prices:
CM1s, PSB Imagine B, and Paradigm Studio 20s are around $1100.
The PSB B6, Revel M12, and Kef Q300 are around $600.
I JUST REALIZED, ALL OF THESE SPEAKERS WERE ONLY 50% BROKEN IN WHEN I LISTENED TO THEM....but I'm guessing I would have the same/similar opinions if all speakers were 100% broken in.
Getting right to the point, I easily chose the Revel M12. But here is why........
I'll cancel out the Kefs first. I listened to the Kef Q300 during a separate listening session in a room that was not ideal. So I might not be giving the Kef speakers the credit they deserve, but they were my least favorite. Smooth because it lacked some high frequencies, but a bit dry sounding. I thought I might have heard some funny noises in the upper mid frequencies and I didn't hear much of a sound stage.
The listening session that finalized my 3 months of speaker shopping was a comparison of the CM1s, PSB Imagine B, Revel M12, and Paradigm Studio 20s. All speakers were right next to each and listened to repeatedly back to back. (for reference, me and my buddy listened to a lot of music by the band "Muse" off of the album "The Resistance". Lots of stuff going on in this album and good examples of sound stage. We listened to other music to verify our findings/thoughts and conclusions)
The CM1s are a smaller speaker, but their frequency response and sound stage were GLORIOUS. The frequency response seemed very even, with just the slightest boost at the high frequencies. Basically a flat response, and I would say that these speakers are tied for 1st place (my opinion of course). Their disadvantage is in the lower frequency range because they are a smaller speaker, and price. (They were also 100% broken in)
The PSB Imagine Bs have GLORIOUS tweeters. Crystal clear in the high frequencies. However, this seemed to be because they were tuned to be catchy. And unfortunately, I did not find the mid and bass ranges to be flat/even or glorious. Of course, if you have these speakers, you are doing very well. Good speakers which have something that the others don't.
The Paradigm Studio 20s were my least favorite. Some of the frequencies and sound stage seemed to disappear. The vocals sounded kind of like they were behind a curtain. But, these speakers sound really good for certain types of music. I'd say they definitely have a niche. Probably country music. Acoustic guitar sounded really good on the studio 20s.
AND THE WINNER IS.......the Revel M12. They were very similar to the CM1s. The CM1s seemed to be just the slightest bit clearer with a slightly better sound stage. But, the Revel M12s are a bigger speaker and provide something that the CM1s didn't in the bass region AND THE REVEL M12s ARE ONLY $625!!!! NOTE: The Revel M12s may not be for everyone. The Revel M12s are flat (in my opinion). And by flat, I mean that I believe they play exactly as the artist intended. But some people will definitely like the "personality" that the other speakers bring to the table. (Example: The imagine B output in the high frequencies really caught my attention.)
The PSB B6 speaker sounded nice and flat, but I thought it had just the slightest bit of tinny (tin can) sound, and I felt the Revel M12 was the easy choice. NOTE: I did not listen to the PSB B6 next (back-to-back) with the Revel M12.
