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

I have refurbished Model 19's and I use Coincident Frankenstein tube monoblocks.  There are two pairs listed right now on US Audiomart and I've had very favorable dealings with the gentleman selling the like new MK III's in suburban Chicago.  The Frankensteins are compact and will easily fit within your limited rack space... not to mention they sound sublime with Model 19's and have an excellent track record with regards to dependability.   They also respond very well to tube rolling to tailor the sound to your liking.   Other quality manufacturers of tube gear that would fit within your limited rack depth are Air Tight and Luxman.   Also, if you stream digital, the Weiss 501 DAC has an excellent remote volume control and can be connected direct to your amp(s), bypassing the need for a line stage preamp.  

@charles1dad

I acquired the Franks about a month ago and the Music Reference RM9 MKII has been sold to a good home. The Franks have proven to be a better match for the Altec’s, as they allow me to hear deeper into the music.

@curtdr wrote:

"If you're intent on keeping the Altecs, OK... but speakers too have come a long way for the money.  If you like lively and yet with that "audiophile classy sound" and old-school looks: Klipsch Forte IV.  aprox $5000"

My Model 19's superseded Harbeth 40.2 Anniversaries and Dynaudio Confidence C4's and I can say without reservation that I get more enjoyment from my 45 year old refurbished Altec's than the well regarded Harbeth's and Dynaudio's... so one should not assume that newer speakers are better or more enjoyable that classic vintage speakers.  If the OP is satisfied with his vintage speakers, I would not replace them with something newer without validating  first hand that newer is automatically better.

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.

So in the last few months, I've demo'ed the following tube amps with my Model 19's:

• Coincident Frankenstein monoblocks (8 wpc)... very nice sound, but not enough power to generate adequate bass
• Consonance integrated with four 300B's (approx. 18 wpc)... not enough power and overall sound was too tame
• Chinese SET integrated with 845 tubes (23 wpc)... wonderful sound quality, but ground loop hum and noise from transformers were show stoppers.  I really wanted these to work as the sound quality was impressive.
• Quicksilver Mid Mono's (40 wpc)... bass was inadequate and dynamics were too tame
• Quicksilver KT Mono's with KT150 power tubes (100 wpc)... Finally, I've found amps with enough power to properly drive my 19's.  I never thought I'd need amps this powerful to drive speakers with such a high efficiency rating.  So far I'm about 75 hours into the break in process, but once they reached the 50 hour mark, I knew these amps were keepers.  Excellent dynamics, plenty of drive and very transparent.

I initially used a Music Reference RM9 MK2 (125 wpc) with the 19's and they sounded very good... but based upon the 19's high efficiency rating, I wanted to try some lower power tube amps.  Little did I know that the 19's high efficiency did not necessarily translate to being able to use low powered amps.  So... based upon my experience, my takeaway is that Model 19's need some power to get them to open up.   YMMV.