I feel it is time to upgrade my 1977 system.......

Try the Rogue Audio Sphinx v3. Tube front end; solid-state power amp. Easy to afford at $1,700. More power than you'll ever need for your Altecs, It has a rather warm sound itself so it might be too much for your speakers.

Alternatively, I'd look at NAD gear. Good quality; somewhat lean, analytical sound that might work well with your Altecs. And nowhere near $18k.

I have to come clean...

While I did like what the Coincident Frankenstein's did for my Altec's, I came to realize that the exceptionally powerful dynamics that the 19's are capable of were missing with the low powered Franks.  So I've sold the Franks and I am on the hunt for a considerably more powerful amp.  I apologize if the OP ordered low powered amplification based upon my previous input.

Head to the local Hi-Fi store and audition as much gear as you can. Ask about hoe demo's also. Folks here are just going to confuse you. 

I bought my system back around the same time, 1976-77 and the Altec 19s have remained quite solid for many years. I did have the driver freshened up at GPA and I did have the XOs recapped by a friend who knows electronics. Basically just new upgraded caps after over 40 years. I drive the 19s with a vintage Sansui G-9000 receiver that produces more WPC than I have ever needed but remains crisp and faithful after all these years. My TT is a Luxman PD121 set up with and external Denon AU 320 step up and denon 103 MC cartridge. I did hear my 19s through a MacIntosh tube setup once some years back and this did cause my heart to flutter but it also caused my wallet to run. Yes, if you have the $$ then do look into a good tube setup and get the XOs updated with fresh caps and that is a rather inexpensive and simple fix. One of my horn drivers dropped the tangerine phase plug when the glue dried out but this was repaired at GPA on both of the 802-8Gs. Altec 19s do like some punch if you enjoy loud music so don't skimp on power even if you buy a tube amp. All my pals who listen to my system just can't believe such great sound comes from gear that is 45+ years old.

My girlfriend has an old Onkyo receiver and JBL floor-standing speakers from the 80s.  I got a WIIM mini network receiver with optical out into a small DAC that goes into the receiver with RCA cables.  I use a streaming app from my phone into the WIIM.  

It sounds really good.