Need a system for Chamber music--ideas?

Another idea would be to go old school - pair something from the Klipsch Heritage series, say the Cornwalls or Fortes or Hereseys with a nice tube integrated. I am listening to the Brahms Piano Quintet on my Cornwalls, which are driven by a PrimaLuna Dialouge 2 as I type this. A set up such as this definitely meets all of your stated criteria, at quite a bit under your stated budget.

Brownsfan: given the nature of the material, Quads would be ideal. And not necessarily new ones. I've owned Quads since 1973, in various iterations, and still have an early pair of the original ESLs as well as a pair of Crosby modified 63's. I haven't listened to them in a while, since i switched to a horn based system back in 2006.
I was stunned at how good a (restored) pair of the original ESLs sounded in Robin Wyatt's room at the Waldorf back in April 2012. He was using a pair of smallish tube amps and a Charlie King built preamp made from old Levinson parts. Granted, the source was tape, which was peerless, but the string tone and elucidation was beyond reproach. The normal caveats about the original ESL are also not problematic given the program material you want to use this system for- the lack of deep bass, the limitations in dynamic range, and the relatively narrow sweet spot. But, man those things are good. Not sure what you have in mind for source and preamp- perhaps the same gear you use for your current system- but worth hearing a good pair. And you can get in (and out)* of them pretty easily if they were properly restored.

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*Most people who have owned the original ESL usually regret selling them and often buy another pair. They should be set up a little higher than the factory feet allow, and placement in the room is critical. They also seem to like small tube amps. My impression- not necessarily shared by others- is that the original ESL's midrange is better than the later 63, even my Crosby version, though the latter is not as constrained in bandwidth or dynamic range. I haven't had hands-on experience with the latest Quads, so my comments don't necessarily apply to the current models. Plus, the old ones are a classic.

Learsfool, its been ages since I heard the Cornwalls. I did not like them with orchestral music, but as a speaker for chamber music they might be worth a listen.
Whart- I really do like the Quad suggestion. As you point out, they are legendary for a reason, and I've always wanted to own a pair. I've always known I couldn't live with them as my only speakers, but this could be the time to pull the trigger. My listening room is already set up around a narrow sweet spot (though the 3.7's are not as bad as previous Maggies). I will not want to change the amps at this time, so they will have to deal with solid state.
Rok2kid and Mr. Tennis-- I did some more listening last night -first to some old Haydn by the Takacs on Decca. I had forgotten how bad the recordings are. I never listen to them. They are miked away from the instruments, so that it sounds as if you are listening to the quartet seated at the opposite end of a tunnel 300 feet away. You get a rather tiny central image with no separation of the players. Next I listened to the Mozart Oboe quartet K370. This is the Linn recording and is very well done. Its close miked, but not too close. Good localization of the oboe and cello, but the violin and viola sound like they are seated pretty closely, so its hard to localize them in space. However, it is important to note that none of the instruments are larger than life, which really makes this recording compelling in its realism. This recording suggests to me two things-- Typical recording techniques are probably adding to the problem, but there may be a limit to what I can achieve with my current set up.

I may suggest the ClasicAudioLoudspeaker T3.4,it is a horn speaker which I have in my bedroom.Fantastic for violin reproduction.Speakers are very efficient 100db/w.m at 16ohms.You can look them up on the web.They are sold manufacturer direct.They will sound best with tube amps.The imaging is spectacular,in my room they are not great for Mahler or Shostakovitch orchestral music but very good for chamber music.

Brownsfan, this thread got me thinking about returning to a project I started
four (!) years ago and put aside. Sitting in my basement is a pair of
MGIIIA'S that I used for about fifteen years until I lost the midrange sections
on the panels due to corrosion of the wire grids. I had very heavily modified
the Maggie's with upgraded xovers, wiring and removal of the socks (which,
no doubt, was responsible for the corrosion). Anyway, I purchased the
rebuild kit from Magnepan and never got around to it. I bring this up to point
out that I am very familiar with the sound of the 3 series Maggies, and
indeed, the sound of these speakers was spectacular in what was, at the
time, an ideal room.

Your 3.7's are clearly a much improved speaker over the stock MG3A.
What makes these speakers stand apart from the Maggies lower in the
lineup, is that amazing ribbon tweeter. The problem with discontinuity
between the midrange and tweeter is much improved with the 3.7's, but it is
still there to a degree. After living with these speakers for so many years I
became convinced that the issue was not one of tweeter level nor xover
point, but of a qualitative difference between the mid and tweeter which
contributed to the problem in the playback of chamber works that you are
trying to solve. I believe that this difference is part of what is contributing to
the lack of separation of the two violins on string quartet recordings. The
violins, having so much high frequency energy, both get "pulled"
towards the ribbon tweeter element regardless of spatial location in the
recording. It's not that the ribbon is doing anything wrong, but that the mid
panel is not doing it as well. I found this to be more obvious on chamber
works than on large orchestral works; although, in those as well, I would
often hear the image of the flute or solo violin suddenly get pulled left or
right towards the location of the tweeter ribbon. Why am bringing all this
up?

Have you considered, as your "chamber music speakers", a
pair of the smaller Maggie's which don't use the ribbon tweeter? You
obviously like the sound of Maggie's, and in many respects even the
MMG's share many of the same attributes as your 3.7's, but in a smaller
package and with, arguably, better integration of the mid and tweeter; even
if the tweeter is not, in absolute terms, on the same level as the true ribbon.
The rest of your gear is so good that a pair of MMG's would probably
sound fantastic, would be easy to move around, and might solve the
problem; and you have a sub that you have already integrated with
Maggies. With a home trial available, you would have nothing to lose. Lastly, if you find they at least have potential, if you are not familiar with
Peter Gunn's mods, check this out:

[URL]http://www.indiespinzone.com/magnestand.html[/URL]

Good luck.