System forclassical music

treepmeyer,  do they currently have in-wall speakers?  or are looking to use only in-wall speakers?   A pair of Magnepan on walls may work for their main listening space. 

Devore Gibbon line (probably used due to budget).
Focused, accurate, produces a wide 3D soundstage with large-scale classical.

It is good to know that there are still a few people who listen to classical music. As a number of other contributors have already said, it would be a very good idea for your friends to visit a local hi-fi dealer and try a few different combinations before deciding. Also, I stongly recommend that they include an SACD player in their shopping list - Marantz make some wonderful SACD players, but a few other brands are also available. Many of the classical music labels (eg BIS, Chandos, Channel Classics, Pentatone) produce outstanding recordings on SACD and of course they cannot be copied so they must be played from the original disc. Having said that, I have found that ripping longer classical recordings (eg opera and long symphonies) often introduces unwanted clicks or gaps in the music so I find it simpler just to play all my music from the original CD.
When auditioning hifi I find it is useful to follow some sort of structure or methodology so I understand the choices I make and end up with a system that is suitable for playing the type of music that I like. These are the tests I use, but I am sure they will be able to think of some tests of their own:
1) Dynamic range. Classical music often has a wide dynamic range and many systems struggle with it. They should choose a piece of music that goes from very quiet to very loud and then back to quiet again. Do they lose detail in the loud passages? If so then it is not the right solution for them. For this test I often use Mahler's Symphony number 2 or Shostakovich's 8th symphony.
2) Piano. For some reason many systems find it difficult to produce the sound of a piano. Again this test will weed out any systems that are not upo to the job. Any piece of solo piano music will suffice
3) Human voice. Choose different types of voice - bass, counter tenor, soprano, choral and ensure that they all sound realistic. Many systems are unable to produce a warm and pleasing sound with the counter tenor and soprano voices for example.
4) Detail. Any recording on original instruments is good for this test. I find the Akademie für Alte Musik Berlin is a good choice but any recoirding on original instruments can be used. You should be able to hear all the instruments clearly and distinctly,
5) Woodwind. Again, the subtle differences between the different woodwind instruments can be hard to reproduce accurately. Listen especially for the oboe and the flute. You should be able to hear which instrument is playing and if you cannot then it would rule a system out for any discerning listener. The Brahms Serenades are a good choice for this test.
6) Your favourite piece of music. It might seem obvious but any music that is a particular favourite must sound perfect on the chosen system.
7) A poor recording. Poor recordings can sound terrible on very revealing systems. Of course we want the system to be revealing but we do want to hear the music and not just the defects.
I hope this helps.
Incidentally the composer in question is Charpentier (despite the fact that it is pronounced Charpontier).

Hegel has a lot of integrated that can be had with built-in dacs. I personally like the Schiit Ragnarok integrated and think that it could be the base for a perfect system for them. Can also be had with dac.

Then add some suitable speakers. I have heard some nice Fyne. F502 might be a good starter. Add a streamer and you have a full system for about $6k or $7k.

https://reviewary.com/fyne-audio-f502sp-review/

https://www.stereophile.com/content/schiit-audio-ragnarok-2-integrated-amplifier

They don’t sound like they are very sophisticated in audio, so I wouldn’t assume that streaming would be the source.  They may have an interest in surround sound, since they currently have in walls and these may be in some type of surround set up (as well as the SACD issue mentioned before).
   Chicago dealers: My current is Simply Stereo, located in the suburb of Palatine
I have also used Saturday Audio Exchange, located in the city on the North SIde on Belmont Ave, and Rouge Audio, on Milwaukee Ave in Bucktown.  Dave at Simply Stereo is a fantastic guy who won’t try to sell them equipment they don’t want/need and will do his utmost to try to integrate stuff that they already have, if that is the way they choose to go.  I have friends that moved into a townhome that had in walls that were of the same vintage you described and that were bizarrely wired (I couldn’t figure it out, at least).  They wanted to use their then current AVR (despite my pleas to junk it, as they could afford much better and are also discerning music listeners) and they were tremendously relieved when he didn’t bat an eyelash when he simply plugged in their AVR after making some necessary changes in their wiring (other people they dealt with were trying to sell them mega bucks systems that was a step to far for them back then.  They have since come back to Dave on their own and started upgrading).
  Finally-if they live in the area, have been vaccinated, and aren’t Serial Killers, I can host them for an afternoon.  I have one “HE” two channel system and two midfi HT systems in my home.  I use digital sources only.  Contact me privately if their is interest