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?

The parasound hca 3500 i have owned it for twenty five years and have never heard or found a better overall amplifier for all speakers. My favorite tube amp is the sonic frontiers for the same reason of i have never found a better one to drive tube friendly speaker and i have owned that one for twenty five years. And for integrated amplifiers my accuphase is definitely the best i have ever had by a long shot.
Several amps come to mind when I think of old amps that still kick butt.  ARC D76 with all the final mods.  VERY NICE.  ARC D79 with all the final mods.  Even better with very good dynamics. These are classic tube designs with a lot of attention paid to details.  They needed regular adjustment to get optimal performance.  The D76 was a great companion to many of the early large speaker systems from Altec, JBL and Bozak.  The D79 was just a great all round amp.  Anything could drive these amps, but the ARC SP-6B seemed the best choice of the day.

ARC D110 (solid state).  Excellent in its day and punchy.  A great companion amp for the larger Fulton systems and speakers with wide impedance swings in the LF..  

And just to add to the mix, a McIntosh 275.  Never really my fav, but a lot of people swore by it.  
Maybe not 'vintage' but I still like the way my Madrigal Proceed HPA2 drives my similar era Aerial Acoustic 7B towers. They need a lot of horsepower and the Proceed seems to deliver.

But my breadth of experience is....narrow.

Regardless, I feel no impulse or need to upgrade. Even if I could afford to.