Old Amps that can still Kick Butt

Not being a believer that time necessarily = progress, I would like to offer the following example of a sonic gem that has transcended time and can totally kick butt in a modern milieu:

The Robertson 4010. I got one of these about two years ago because it was in immaculate condition, the price was so low and I was inquisitive. I hooked it up and let it warm up for a couple of days. OMG this thing was in the super amp league: Transparency to die for, slam that you couldn‘t‘ believe for for a 50W amp.. Peter Moncrieffe wasn‘t wrong in his review of this amp: this thing is in the Sterreophile Class A component category hands down. Even after all these years.

What amps have you encountered that have defied time and can still kick butt today?

I also have a Scott Lk-150, and it is a special amplifier. It’s my “back up”, but I’ve tried it in my main system in place of a very well respected, current model amp, and it competes very well. I actually prefer it with some music. I took it with me to audio stores to compare to new amps when I was looking to buy. It sounded better than all the ones I auditioned. We’d listen to the new amp first, then put the Scott in its place and listen again. I could tell the moment the salesman realized the 60 year old amp sounded better… his jaw would drop. Literally. It’s also gorgeous to look at. I haven’t heard everything out there, but I’ve owned dozens of amps, and I’ve listened to many dozen more. Something about this Scott just sounds “real”.
I am listening to Three Chords and the Truth by Van the Man on a Cary SL-100 / Adcom GFA-535ii combo and can find no fault. Not pushed hard, the little 535 is no slouch. It drives the large Advents really well.
Love questions like this, great question, interesting answers. Lots of good info.

I have an Adcom 555II that I am trying to decide whether to rebuild from the resistors up, not just the caps. Nelson Pass design, how bad could it be with a soft start circuit added into it?