MoFi or Harbeth (used)

Hello Hugo1.  I never heard a Harbeth I didn't like. Hard to go wrong there. Happy listening.

I’ve heard both.  Mofi probably more bang for the buck.  

I have the Mofi 10s, love them but they are BIG so not really 'bookshelves'. Very sseamlessly coherent speakers with a natural tonality.

Harbeths are an acquired taste IMO and are picky about music and electronics, the Mofis very accommodating with just about any genre and gear but will reward expensive electronics.

However the 10s have crap resale value, for some reason Mofi have begun discounting them, so if that's important to you look elsewhere.

@panzrwagn I am 100% right if the line source ends at barriers like the floor and the ceiling. The line source behavior then extends down to 1 Hz. As you note, line sources project power better and are used exclusively at large concerts. Their vertical dispersion cuts off sharply so they curve the arrays to cover the height of the arena. In my instance the line sources are dipoles and their horizontal dispersion also cuts off sharply. The Sound Labs are therefore curved to cover a 45 degree arc. The advantage of this is much less room interaction. I only need sound absorption directly behind the speaker. 

The baffle effect may add 6 dB but the volume still drops off at the square of the distance making it more difficult to hear the speaker farthest from you. 

You might be interested in this https://imgur.com/gallery/building-resonance-free-subwoofers-dOTF3cS  These were not designed to be high output. They are - 3 dB at 20 Hz. Their sensitivity is 89 dBSP/1watt/1meter. Getting the right bass response still requires a lot of power and digital signal processing. 

Did you get to see the concerts you rigged? The most insane bass rig I ever heard was Stanley Clarks line array with RTF back in the 74. Must have been 30 feet tall. The most incredible bass I ever felt was Les Claypool with Primus at Red Rocks with one exception, Jerry Marotta's Bass drum in Peter Gabriel's Security Tour. It hit so hard I was getting nauseated!  

I recently got a pair of MOFI 10s new from The Music Room at a big discount. I heard them at the Tampa audio show  2 years ago and was very impressed. Andrew Jones was using the HiFi Rose 250 to drive them which i think is 200watts/channel.  They have replaced a pair of Klipsch Heresy IV speakers in my 14 x 16 room. They are a much more rounded and satisfying speaker in my room than the Heresys (which I did like).  I am powering them with a Bob Latino 120 push pull tube amp and have not had any problems driving them. At the price you can get them for now, I don't think you could go wrong.