Recommended speakers around $10K used

If you are looking for midrange with overall coherent sound and have the proper space to place bipole speakers you should listen to soundlab's larger electrostatic speakers or an innersound eros mark 2 or 3 (which have a narrower sweet spots). I use small maggie 1.6 speakers but the larger 20.1 model will have plenty of bass if you have plenty of space. As you can tell, I prefer planar speakers to horns and cones but room set up is paramount in getting the proper speaker performance.

For guitar reproduction and imaging, check out a planar speaker. I would highly recommend checking out Wisdom Audio M-50 for your set up. I had a similar set up with my M-50's separated by my equipment. They would rival the Megalines but beat them out when it comes to acoustic guitar music especially slack key styling. The detail is phenomenal with the planar magnetic line source and the 12 inch woofer captures the bass. One disadvantage though could be that they require bi amplification. Worth listening to!

gradient revolutions

I do not claim to have a golden ear, but have listened to several speakers on your list. I play guitar, so the sound of guitar is important to me too.

Revel salon auditioned in a room with some treatments on the walls, but other speakers in the room too (so a suboptimal setup) with levinson monoblocks (I believe no.436), krell preamp and a denon cd player. I don't know if it was the denon or the room or the fact that the salesman disappeared (I didn't know if the rear tweeters were on or off, etc), but the imaging wasn't comparable to the others I'll comment on below. The bass was great. Everything else sounded a bit subdued. Salons do have adjustments for bass and tweeter level, but I didn't know how to adjust them.

Wilson sophia auditioned with meridian 800/861 combo and classe cam 350 monoblocks in a dedicated treated room. Sounded great to me on acoustic and electric guitar and imaging was great. I have since listened to watt puppy 7 and alexandrias with krell amp/ vtl 7.5 and halcro preamps/ wadia cd player in a lightly treated room and the sound was totally lifeless and inorganic. During the sophia demo I also listened to Maxx 1 and WP7 and sounded MUCH better to me with the meridian/ classe combo.

JM lab alto utopia beryllium auditioned with meridian g series preamp, cd player, and amp. Imaging was great, sounded great for acoustic and electric guitar. Not quite as dynamic and "raw" for electric guitar as the wilsons, but could have been due to smaller amp, etc.

I also did demo on b&w nautilus 801(before diamond), and martin logan ascents, odyssey, prodigy. I was not impressed at all with the b&w, but source for all of these was a musical fidelity integrated amp, so likely didn't have enough juice for them. Martin logans sounded awesome to me for acoustic guitar and vocals, but sounded fatiguing for electric guitar after about 10 seconds. Each larger logan had better bass than the other. Logans apparently are very finicky to setup, though and likely this played a role.

Hope this helps.

Wilson Benesch ACT speakers.