These are some great responses and you've all shined a light on possibilities that I hadn't known of or considered.
There were a few suggesting that just servicing my MAC6700 may be the way to go. Here's the story:
I had a milestone birthday 11 years ago. I had always wanted a McIntosh system and the 6700 was newly introduced just then so I thought it to be perfect gift to myself; I was delighted with my purchase - amazing sound in every dimension. The unit came with a 3 year warranty; one month past that, the right VU meter quit. Mac was good enough to pay my local service guy for the repair so no big deal. Not too much later, Microsoft stopped Windows 7 support so I had to upgrade my music server to Windows 10. It turns out that Win10 is incompatible with the Mac hardware driver - the system crashes after about 5 minutes. I think I may have been one of the first to alert Mac of this problem - there is no solution nor does Mac intend to work on a fix. In desperation, I had my service guy upgrade the Mac firmware; no luck. So I've been using an outboard DAC (Schitt modi); huge performance drop. (btw - I also tried to make the onboard DAC work with Win11 and IOS, no good). About 2 years ago, the dials stopped working. I called Mac, and arranged to ship it to Binghamton for a thorough going-over. 11 months later and $1000 lighter the unit returned with many, but not all of the issues I had identified resolved. Mac also fixed a few things that I didn't know about. Not long after, the tuner started fritzing again and the remote stopped working. I ordered an updated remote from Mac...it's OK, but is not a complete match to the original. Bottom line: the legendary McIntosh quality that I thought my $6700 would buy 11 years ago is not in evidence. As they say: "this is not your father's McIntosh". In short, I'm reluctant to spend any more money on Mac stuff. An aside: the HK 880 VXi that I bought sometime in the 80's and that the Mac replaced is still running strong in another location.
grislybutter: the "box of nails" sound is not what I'm looking for. Thanks for that. Message received.
yyzsantabarbara: a good used tuner is an interesting suggestion. I've come to really like HD fm; my MAC6700 has that feature enabling really good fidelity and some additional sub-band stations. In my view, it's a technology that hasn't been pushed effectively. It's curious that later production MAC6700 units do not feature HD nor does the MAC7200 (at least when I last looked). I do appreciate the suggestion, however. One that I hadn't considered....maybe I will.
lig98ljk: I'll look into Motiva, I think it's class-D though.
yogiboy: I'll look into Magnum Dynalab. There's a dealer near me. I have to admit I've not heard of them before your suggestion.
Thanks and best to all!