Bookshelf to replace Martin Logan Source

Thank you all for your recommendations! Investigated all and have the following comments:

bdp24, thank you for recommending Eminent LFT-16A. The look really appeals to my (science experiment) design sensibilities (looks like something I would build). Also a fan of alternative driver technologies (getting away from domes). Price is good. Seems best matched with warm electronics (not sure where NAD C388 is on warm/bright scale) to offset their bright tendencies, combination of 8ohm and low sensitivity is not ideal (this could be argued otherwise). Ultimately, for me - a contender, but not top of the list.
Eminent LFT-16A: 8 ohm 3-way, 85dB/1w/1m, +/- 4dB 45Hz - 20kHz

grinnell, thanks for Ref 3A de Capos (currently MM de Capo BE) recommendation. These are interesting, made me think about the idea behind sloped front bezel (not uncommon) for correct time alignment.
-Random thoughts:
Doesn’t that also make the drivers slightly off-axis? Wouldn’t it be better to back-set the tweeter relative to the mid/bass and maintain correct axis? Maybe ’pointing’ the tweeter apex up above direct line of listener’s ears helps reduce sharpness (alternate form of apex dampening). This would likely be particularly beneficial with beryllium.
-End random thoughts.
The 8.25" mid/woofers have no crossover, and I like that (fewer/simpler crossovers the better), reviews agree - they play deep, on the expensive side. They answer the difficult request for bass from a bookshelf.
Ref3a MMdeCapoBE: 8 ohm 2-way, 92dB/1w/1m, +/- ?dB 42Hz - 40kHz

jrpnde, recommends PSB Imagine B. Another great-looker, really like the rounded cabinet. Favorable spec’s, well under $1,000/pr, everything to like.
PSB ImagineB: 8 ohm 2-way, 89dB/1w/1m, +/- 3dB 55Hz - 23kHz

DavidGWillett, I never heard of Watkins, and the Gen4’s seem like a great choice. Reading through the website, really like what they’re doing - focused specifically on 2-way bookshelf, with an abundance of recent awards for their efforts. 1st-order crossovers with only high-pass capacitors (no coils or resistors = simpler crossover, same a Ref3a deCapos above) is good. Spec’s say they play low.
Watkins Gen4: 8 ohm 2-way, 88dB/1w/1m, +/- 2dB 41Hz - 20kHz

plinytheelder, Martin Logan Motion 15 is interesting because I’m a ML fan (besides ESL Source, HT is made-up of dual SLM-XL as center-channel, 4 ML CI-** in-ceiling). It reminded me of a forgotten contender, ML 35XT, which I had mean to investigate. So glad you mentioned ML! 35XT is step up from Motion 15, so consider 35XT. Revel m103 are -3dB @ 59Hz... don’t extend low compared to others in this group.
Martin Logan 35XT: 4 ohm 2-way, 92dB/1w/1m, +/-3dB 50Hz - 25kHz

sixsigmaguy, Quad Z-2, now those are beautiful cabinets! Nice and curvy with an expensive-looking finish. Big ribbon tweeter (sound like ESL) and carbon fiber (light and rigid) mid/bass. Sensitivity is low.
Quad Z-2: 8 ohm 2-way, 84dB/1w/1m, +/-3dB 50Hz - 20kHz

elliottbnewcombjr, recommending B&W DM100i, those are some ugly speakers. I have mixed feelings about B&W that haven’t quite come to grips with yet - they challenge my basic musical preference (what sounds good to me?). Audiophile types will say something like "You either like surgical accuracy, or warm rolled-off highs." Then there is the term "neutral" floating around. Some speaker brands signature voicing is bright, while others are warm - as intended for their customer base. B&W tends to be on the bright side of neutral. I think this is because of the hard-dome tweeters that produce surgical accuracy, and occasionally (to some people’s ears) a piercing sharpness. This makes them fatiguing to listen to for long periods. On the other side of the spectrum is something like ML ESL’s, which are warmer with ’rolled-off’ highs (some call ’natural-sounding’). I have a set of FPM4’s on the optional table stands, and have been using these (along with a sub) for 2-channel music. They have become my reference set for others (Elac D2-6.2 and SVS Ultra) to be judged against. Over the years, I have always considered them too sharp, and at times have hated their sound. Hated it enough to replace them with ML SLM-XL’s in the HT (that’s how they ended-up in the 2-channel room). But comparing them to newcomers, (with a sub) they sound very good. This has made me realize why some people like the accuracy - because you hear more detail... detail missing when other speakers are playing the same track. Whenever I’ve demo’d B&W in a store, they always sound too sharp (same as DefTech), same as horns always sound like horns to me and I lose interest. So while I’ll say I prefer hearing the details, and FPM4 are better at that than SVS Ultra BS, another aspect is the sharpness that can sometimes be painful from those hard dome tweeters. Think my best bet is to stay true to what I know works for me - no hard domes, no horns, no size large t-shirts (they’ll always be too tight after the first washing - how many times have I re-learned that lesson).

Thanks everyone for the recommendations! So far order of interest is:

Watkins Gen4 $2500/pr: 8 ohm 2-way, 88dB/1w/1m, +/- 2dB 41Hz - 20kHz
Ref3a MMdeCapoBE $?/pr: 8 ohm 2-way, 92dB/1w/1m, +/- ?dB 42Hz - 40kHz
Eminent LFT-16A $1250/pr: 8 ohm 3-way, 85dB/1w/1m, +/- 4dB 45Hz - 20kHz
Martin Logan 35XT $1,000/pr: 4 ohm 2-way, 92dB/1w/1m, +/- 3 dB 50Hz - 25kHz
Quad Z-2 $2550/pr: 8 ohm 2-way, 84dB/1w/1m, +/-3dB 50Hz - 20kHz

Following up.

I did try the ML LX16, very affordable, didn't compare favorably with other bookshelves in the stable at the time (SVS, Elac, B&W, Buchardt), they did sound better than Micca. The cabinets were beautiful, and I really liked the grills (cat-proof). To me, LX16 (and the entire line of Motion) sound like the cabinets are made too thin or not braced enough internally - resulting in cabinet resonance. I always hear the cabinets when listening to ML box speakers, and LX16 is same.

Also tried Buchardt S400, and those are wonderful speakers. They compare favorably to SVS Ultra Bookshelf. After extensive A-B between SVS and Buchardt, decided the high frequency detail and much lower cost of SVS gave them the win.

Then I abandoned the search for best bookshelf and purchased $120 pair of Polk T50. They are essentially a two-channel bookshelf with two passive radiators added to form a mini tower. I'd never heard Polk, and the price was right for demo. The little towers sound awesome, easily besting all (even ML electrostats). For a small to medium-size room - they must be the best bargain ever. Soundfield is wide, detail is there, bass is adequate, tonal quality is outstanding. I have them setup next to ML Source, and occasionally A-B switch between them. If you hold your head just right, Source sounds a little more 'airy' and fuller midrange, but T50 sound great everywhere in the room and without rolled-off highs.

Polk T50, inexpensively bests many others. They have become my reference set for 2-channel listening without a sub. Second place goes to SVS Ultra Bookshelf due to value - you could buy eight pair of T50 for the cost of one SVS pair.

@argonatz The Polk T50 are a terrific value. I think there are other options in the same price range that might compare favorably. Check Audioholics website for shootout that includes T50 and similar competitors.

My T50's ended up in my son's system with an old Sony receiver and CD player and BT receiver (for streaming from his phone) - seldomly used.

For my 2-ch system, once I decided to move to floor-standers, built LinkwitzLabs LXmini speakers. Continued AB/demo testing many more against LXmini, which ultimately included Tekton Double Impact (with factory upgrade). LXmini performance has exceeded everything - sold all contenders, including the Tektons, and ML electrostats sold a few months ago. I did use those two (and the B&W currently for sale) as my 'references' for a while to judge/voice against LXmini. Then about a month ago, I built a pair of dual 12" open-baffle subs to compliment the 'minis. Now, I feel the sound is perfected, and I've refocused on gear to simplify and raise the 2-ch system to the next level.

Polk T50 are an extraordinary value, but check competitors first. Also I bought them on-sale at Amazon, I recall them being super cheap - wait for the sale unless you're impatient.

If you want simple great value, stick with the T50 or contenders (LXmini is not simple). If I recall correctly, in the same price range are Sony, Pioneer, and Dayton Audio (PartsExpress) - all have an excellent value offering. Think the Dayton Audio comes out on top with reviewers ( I have no personal experience with them) - think it was the MK442T.

LXmini requires commitment. They are DIY only (unless you buy what someone else made), Also requires DSP and multi-channel amp (unless you build a special passive crossover). Those aspects are also strengths, depending on one's point of view. The sound is holographic and most similar to electrostats and bipoles (speakers with additional drivers on the back side). They sound like hearing the performance live. LXmini's are brilliant, and designed by Linkwitz (of Linkwitz-Riley crossover fame), a genius in many aspects - may he rest in peace.