Best vintage amps (late 70s / early 80s) under $3k?

Well of the things that I've heard from that era,  some already mentioned. 
Ampzilla.... Although the Son and Grandson sound better. 
Any of these with updated parts are excellent. 
Heathkit  AA-1600 & AA-1800.  Marshall Leach Amps, same as the others, with updated parts,  surprisingly good
Sumo Nine... Same, New power supply caps, replace most of the ceramic disc and this is an amazing amp today.  
Sumo Andromeda,  More power, but in my opinion, not as good as any above.  Odd because the Nine updated is probably the best by a small margin. 
Dynaco ST-70  in Tubes and ST-410 in solid state.  
SAE Mark series/00 series and 01 series... (not all, but many are really good with some decent parts upgrade. 
Sony TA-N80ES  excellent
I'm sure some would say Hafler... DH500,  I Had one,  it was ok
Eagle Kinetics pretty good
The Pioneer M22 has been mentioned, didn't have the power of the Spec's but sounded much better. 
A lot of people liked the Yammys… not me
Kenwood L07M.... really not bad 150 watt mono amps
The Carvers of that Era, I did not like at all
The Adcoms everyone knows those 
Phase Linear... several liked them,  not my cup of tea 
Kinergetics Research was certainly decent to very good depending on model. 
Nikko had a ton of Amps, I've heard at least 1 that was pretty good and 1 that WAS NOT... sorry, don't remember models. 
Amber 70 was a decent sounding amp
Threshold had a couple of good amps then... 
A lot of people like the big Rotel amp out then.  I thought it was mediocre
Of course Krell had the big KSA amps out,  they were good
Harmon Kardon… Don't remember, but one of the Citation amps was good
Ok,  I'm blanking on any more for the time being,  maybe more later

Thank you, timlub. Anything specific from your list that sounded like the M-22 on steroids and didn't run hot? That's what I'm after, ideally.

pts....you can look for a Pioneer Series 20 M25, which shares the family sound with the M22, but having both, I would still stick with the M22. Once you go class A, it is hard for your ears to adjust to anything else. You and I both know the sonic wonder of the M22. There was a poster ( porsche something ) on the Tekton Double Impact thread that used an M22, and found something else to replace it, but if I remember correctly, it was also heat producing. I will gladly purchase your M22 when you are ready to sell, lol. P.S. : When I owned my M22, and I had a few of them, I changed out the ac cord to a much heavier gauge, it it made a wonderful improvement. I also believe the bias can be reset, taking it out of class A, and giving it more output, which is something to consider. Good Luck....Enjoy ! MrD.

I’ve spoken to someone who had an M-25. More power, inferior sound, and unfortunately just as much heat.

I know the guy who had the Tekton and M-22. He ended up getting a Don Sachs tube amp that he prefers. Tekton are very efficient speakers though, I used to own some.

I got a super experienced tech to refurbish my M-22. I asked about a new power cable, and he said "the line cord does not drop voltage when the power increases as it does in a class AB amp, so increasing the wire gauge buys you nothing. On the other hand, there are better quality line cords available. But again, I think the improvement will be subtle"... so I gave it a miss. I did get some Mundorf caps installed though, which are very nice. Gives the top end some sparkle, I think.

I concur with the recommendation to take a good look at the NUForce STA200 SS amps.  Check out the reviews on Absolute Sound, Hi Fi News, Stereophile, and the Audio Advisor website.  They have reduced the price to a rediculous cost as low as 449 each (Audio Advisor yesterday).  At 499 I purchased a pair to bi amp my Martin Logan SL3 electrostats.  I previously ran class A Stereophile recommended Creek 5350 SE’s, or alternatively a pair of restored and tweaked Harman Kardon Citation II tube amps that I spent a lot of money to completely rebuild and installed the best components and tubes available.  They sound awesome, until I acquired the NUForce STA 200’s.  They retail for over 1200 and were considered a bargain at that price, the sale price is rediculous.  Some pretty strong statements from users, that I agree with after they hit 20 hours..  My pre-amp is a tweaked out PAS-4 Dynaco tube (Panor 1995yr version) with the best Mundorf Supreme caps EVO Silver, gold, oil and using Vishay low uF bypass capacitors to refine the soundstage and the best tubes available including a quad of the HG Russian ‘75 6N23P’s and 60’s Grid Frame E83CC Tesla’s ( TeleF 803S grid frame copy) in the front end of the phono section.  The ML SL3’s electrostats have large panels that are extremely resolving to reveal the finest details.  There is no question to my ear that the NUForce STA200’s live up to the accolades  in users reviews and outperform anything else I’ve connected them to.  Fast, resolving, broader/deeper soundstage, clear, dead quite, unfatiguable.  And they run cool.  Eclipse my Creek’s and the HK II’s by a large margin that is very audible if not impressive.  I’m 65 yr old and have been running audiophile systems since I was 15 with my first tube Mac (cut a lot of grass for that).  I never thought I could be torn away from the tweaked HK Citations’s, but these NUForce amps are the best audiophile bargain and they are bran spanking new.