What constitutes a great solid state power amp?

Can you see any "common patterns" or simularities between great power amps,e.g. only one pair of output devices or a lot of them, little or no nfb,global or local nfb, over-dimensioned power supply etc?
Any idea of what traits in their performance that are of greater or lesser importance?
Of cource, this is indeed generalizations, and at risk of beeing overly simlified,but...

My own view is; type of otput devices(ss) are of less importance,but just maybe bipolar have an advantage here.
The amp´s ability to handle transients are more important than very low THD figures.An amp´s ability to handle back-emf from the speakers, is of very high significance.An amp has to be sufficient linear, before applying any negative feedback at all.

There are , -strange enough, no real valid measurements to predict how an amp will sound, at most some cues. Amps are often constructed in a rather traditional way, even if their creator tells you how radical they are, i.e. it´s more about evolution than revolution.

Some days ago, I read a review of the DarTZeel NHB-108 power amplifier,in (the English magazine) hi-fi +, and also read about it at the manufacturer´s website.This amp could be very good, but I disliked some categorical statements on the website(even reflected in the review);stating that something is nearly perfect,doesn´t make sense to me.
IMHO it´s very much about which compromises you make, as the constructor.
SS power amps rarely garner the kind of romantic associations some other components attract. So long as an amp acts the strong, silent type that's about the most I hope for. Better units share common characteristics. Over the long haul, here's my bare minimum requirements: a torodial transformer and rows of external heat sinks. Expensive parts seldom find their way into underperforming products. Couple those two must-haves with a weight of at least 50 lbs. and gold plated input connectors and I'm set. Beyond that, a reknowned designer, Class A operation, dual transformers, and balanced topology indicate the very best. What about specs? A reliable measuring stick may be an amp's popularity with buyers. If a manufacturer sold a bunch of them they must have been doing something right.
Simple --one that sounds great and is both reliable and affordable!
I have a Classe DR-9 amp built by Dave Reich. This amp to my ears sounds great and so far" from my mouth to GODS ears" is very reliable.I believe this amp can give many modern ss amps and many tube amps a run for the money. They can be had for a fair price. But lately I see alot of DR-9s going for unreasonably asking price's on Audiogon. A grand or under would be a very good price for this well built amp. Just my humble opinion?