20 Year Old Amplifiers compared to 2017

what changed...
90's to today? nothing.
70,80's vs. 90's yes. changed a LOT.
If you open user manual of 1980 equipment and 1990+ equipment you will see HUGE differences.
First off circuit, block diagram, service manual isn't published anymore. That is due to I guess depletion of normal human intelligence or something stimulating that depletion. If earlier people were smart enough to get to the bottom of problem by reading service manuals, now they can't. Now they get zapped and sue the manufacturer so service instruction ain't no good no mo pal since 90's. 
My solution to this problem is using and servicing units that have circuit diagrams and user manuals and let the rest of crap disposed. So I assume nothing can possible beat 80's units that are the most advance, well built and serviceable. 

My take is that this one of the most informative threads on AG in a while with very thoughtful responses. I recently got an First Watt F5 amp, my first Class A amp, and it is a glimpse into music that I had never heard before.  I dunno if all pure Class A amps have similar performance to the F5, but it is the pinnacle of amps I have had over 45 years.  It is not as powerful as my McCormack DNA .05 amp, a Class A/B amp, but between the two of them, I am very happy.  I would be very keen to find an upgraded Krell KSA-250... it is the one Class amp for which I lust. 

I am a denier of the SQ benefits of Class D amps, but I have not heard the best of them. The ones I did hear seemed to be bereft of the total musical involvement I enjoy with Class A and Class A/B amps.   I am a lover of vintage gear myself.  Again, this a great and informative thread. 

@whitestix 
Believe it or not, there's room for improvement with the F5. I've been tweaking and tuning mine since we last crossed paths. I replaced some shielded interconnect cable with some solid twisted wire for the input signal, replaced the silicone MOSFET insulators with split micas, dialed in the distortion a bit better, and cranked up the bias to 1.4 amp. This amp now delivers a 62 watt class A envelope into 8 ohm. The power is hardly the best part though. The thing with the F5 is you get pronounced sonic benefits as you crank up the bias until you get up past 2 amp. I doubt I'm going to squeeze more bias out of it in this chassis though. 
This thing has made me a serious believer in simple, heavy, high bias, class A amps with obscene power supplies. 

I imagine that Nelson underclocks the First Watt amps to prevent them from competing with Pass Labs. 

My Julius Futterman OTL3s are circa early 1980s. I recently had them converted from pentode to triode, and replaced all the caps with Jensen foil oil caps. They were tuned to my Altec 694Cs and to my room. 

I cannot imagine anything sounding significantly better for the money.