Avantgarde Uno/Duo

Since the bass units are self-powered, the main amp doesn't have to be solid state. In fact, although there are a few different owners here who have used them with solid state, I've gotten pretty remarkable results with the Lamm SET. And, because one of the advantages of this design is extremely high efficiency, it's a perfect opportunity to use such a low powered amp.
If you get a chance to hear the latest versions at a dealer (I think Rhapsody in NYC may be your only option in the NE, not sure), post your impressions. I don't know if he is wedded to Avantgarde's amps, but you should get a chance to hear them with a good SET rig as well.
Good hunting!

Agree with Whart's observations. I have used Jim Smith's Get Better Sound's recommendations for speaker positioning and that helped a lot. These speakers require considerable up front care and feeding to get them sounding their best but feel like it is worth the effort- even fanatical measurements down to an eighth of an inch. Maybe I am just used to them but do not hear discontinuity that some have reported. IMO their strengths outweigh any downsides. I will say that when I went from the Duos to the Duo Omegas there was a significant improvement in overall presentation, including top to bottom integration. In fact I would say that it was probably the largest improvement of any upgrade I have made. I haven't heard the newer models so can't comment there. They do well with tubes and my system has tubes in the pre, amps and phono pre. I would guess that a large percentage of AV owners use tubes.
At one point I looked into some of the new technology like DEQX for improving both speaker and room acoustics but became quickly overwhelmed by the challenge. That may be the future though.
Good luck with your search.

The Duo Omega has a lower mid-range crossover frequency which can help to reduce mid to bass integration issue. If you don't listen to vinyl, I think a digital processor can also help. In addition, the digital processor can also correct the driver time alignment. If I do get the Duo, I will use my Tact 2.2XP to set the crossover between the sub-woofer and mid-range horn. I suspect digital processing is one of the directions that Avantgarde is heading as can be seen in their introduction of Zero One.

Whart and Inman29 have pretty much nailed it, but with proper setup (including minimum 12' distance from listening seat to drivers) the integration is a non-issue (I have Duos which I upgraded to Duo Omegas) and the active woofers have level and xover frequency controls so you can dial in the transition properly.

I also second Whart regarding amplification; the raison d'etre of these speakers is to allow us to use SETs without any practical SPL shortcomings. I've had excellent results with a little as 3.5 WPC (the Omegas are 107dB sensitive). Apparently Avantgarde feels otherwise, or perhaps it's simply that their in-house electronics design expertise is in the solid-state realm.

Mine speak with a single voice and are so "alive" that cone n' dome speakers just sound lifeless to me. The only way mine would ever leave is to be replaced with Trios/Basshorns.

YMMV of course. Good luck in your quest, OP.