Classical speakers that do violins well??

Mrtennis...4 ohms is a lot for the MG1.6, although that value would be in line with what many speakers use when trying to hush up a dome tweeter to match the typical woofer. Since Magneplanar designs and builds both the woofer and tweeter parts of the MG 1.6 they can get the efficiency to match better than a manufacturer who uses off the shelf drivers.

I settled on 1.5 ohms. However, I have also replaced the stock iron core crossover inductors with #10 air core inductors having less resistance, so my woofer efficiency is a bit higher than stock.

Telarc use ATC SCM Active 20's - another brit speaker to add to your brit audition list suggested above. You won't get an active version and a massive sub at your price point but a used passive SCM 20 should be within reach and get you started towards

nothing more than the faithful reproduction of the tone colors of unamplified instruments

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If it is good enough to keep Telarc engineers happy then it may be what you are looking for...

Good Luck!

What are your speaker + listener placement constraints (distances to walls/speakers), room dimensions, and acoustic conditions like?

These things have at least as much to do with what you're hearing as your speaker choice. Placing your speakers within a few feet of the front wall will get you a low frequency boost that will move up into the midrange as you get closer. Sitting too close to the wall behind you will do the same thing. A room that's overly reverberant at high frequencies, TV between the speakers, or coffee table in front of you can get shrill.

You really need to optimize the speakers + room as a system. If you're stuck with the speakers being too close to the front wall you want to be looking at on or in-wall designs that take into account the low frequency boost. If you're sitting far from the speakers something with more directivity (horns) will help retain clarity. Etc.

Spica TC50 or Angelus are very good at reproducing the tonality of strings without harshness, are not bloated at all in the bass (the Angeluses seem to have a bit of a dip in the mid bass, but strong low bass). They do have their weaknesses, though, in terms of high frequency extension, dynamics, resolution, and ability to play loudly. (Perhaps this is a speaker that even MrTennis could like?) Plus, they are very inexpensive. Also consider the Audio Physic Virgo II. I've never owned a pair, but remember them in the showroom as one fo the best all around speakers I have ever heard. I liked the Magnepan 1.6 QRs, but could not get them to work well in my room. I also listened to the next model up in the Magnepan line, and thought its tweeter wa way too revealing - every cymbal strike sounded like somoeone throwing a fistful of gravel at the cymbal. More shimmer than you hear in real life.

Check out the Tonian Acoustic loudspeaker
The fostex driver makes instruments sound so natural

Bass is pretty good as well for a small monitor