Higher Efficiency Speakers

Being open on two sides, rather than a square(13.5 X 13.5), is an acoustic benefit. I used Maggies(SMGa/MG12/1.7i), for decades, in an actively bi-amped systems, with tubes on top. Recently, I purchased a pair of Emerald Physics’ systems, and won’t be looking back. Much more efficient, with wonderful imaging, immediacy and tonality. The other choice/option was finding SS main amps(more juice), that could match the transparency and sound stage depth(etc), that my modded Cary’s provide. That would have been too expensive. Make it easier, on your excellent electronics. Then again everyone doesn’t enjoy pretending they’re at the original recording venue and attendant SPLs(I like to feel the music).

With that small of a space you might want to make sure whatever you get will work well close to the wall behind. That eliminates anything that fires or ports to the rear. So no dipoles or rear ported.

Larsen supposedly makes a speaker or two intended to be close to the wall. A number of friends heard them last year at a show and they were the highlight (Capital Audio Fest). I normally wouldn't mention something like this, but when ten people rave about the same item at a show, that's pretty interesting and rare. I've never heard them, but could be worth looking into. 

There's a used pair of Vandy 5 from a legit seller listed here for $4k, pretty tunable for the room and very good speaker overall. Visuals on the pair aren't ideal, so buy 'em and dim the lights ;-)  Cheers,
Spencer

While I love my current (and I hope final) system, If I had it to do over, I would go with high efficiency speakers (100 db+). They give you so many options in amplification. I'd love to try the Pass Labs XA25, 300B amps, etc.. And they still let you use high-power amps. Very versatile. 

Audiokinesis speakers are terrific and are commonly married to Atma-Sphere. Duke LeJeune has great taste in sound. They are front loaded horn hybrids but strike me as a blend of a wave guide, although I may stating this out of turn. Fatigue free sound with option of an even sound distribution like dipoles. 

Devore...