Anything more resolving than 65 year-old speakers?

My experience with Quads is extreme listening fatigue at volume.  I switched to Maggies and got all the accuracy without the fatigue.  Of course, you need excellent hardware--typically tube--and they have to be set up properly.  I have never found anything more accurate.

As for the HQD system, we made some of the stands for him and some 24" Hartley sub cabs--HUGE and heavy--they were on 4" casters and made out of either 1.5" or 2" composite board--I forget much of 1973-76.  Unfortunately, the ML HW of the day was un-listenable even though it was made with the best possible parts and designed by a terrific designer.

As for horns, they belong on the top of poles at HS football games, not in your home system.  Put a pair next to a pair of Maggies and see what YOU think.

Cheers!

Very happy with Sonner Legato Unum and QLN P3 in my system. Both driven by tube amplification in both settings. 

Brings to mind the fact that sand amps and push-pull tube amps suffer from odd order harmonics. I have totally eliminated that from my life for a couple of years now and if I ever hear any TV or stereo of that degraded nature, I immediately notice how unnatural it sounds, which, of course for classical music is an absolute disaster. 

Here is the link to odd order harmonic graph: https://www.decware.com/newsite/TORIIJR.html

I have a pair of Altec Lansing 604Cs. 
The serial number dates them at 1956, two years younger than me. 

To paraphrase a famous Beatles song:

604Cs are good to me, you know
They make me happy as can be, you know
I say so
I'm in love with them and I feel fine.