Synergy

It’s been brought home to me lately the dominance that synergy has in the performance of a HiFi system. My many years old Class D NuForce monoblock amplifiers broke down recently and appeared unfixable. Thus began the search for a replacement amp.  I began with what I thought would be a temporary cheap returnable replacement for my monoblocks while they were in repair: a $450 Optima NuForce (different company from my original NuForce which went out of business) class AB amp.  To my surprise, the sound wasn’t bad at all.  Although not as detailed, the general contour of the sound was really well balanced.
When I found out that my amps probably couldn’t be repaired, I started a quest for a replacement.  I thought it wouldn’t be hard.  After all, if  the cheap Optima amp sounded so good, it would be a cinch to get a better quality replacement if I spent more money.  Boy, was I in for a surprise! 
I returned the Optima and started with a new pair of Red Dragon monoblocks which were recommended on Audiogon and highly reviewed elsewhere. For three times the price of the Optima, they had to be great. Well, in short, they weren’t. They had good detail and  bass output, but were in no way natural sounding.  The Optima surpassed them in tonal balance.
After much soul searching in looking for a different amp, it was highly recommended, again on Audiogon, by two people whose opinion I respect, that I get a Belles amp.  So, I returned the Red Dragon and then bought the class AB Belles 150A amp, used, for 2x the price of the new Optima.
It was better than the Red Dragon, but lacked bass and seemed to not have enough power.
I returned the 150A and (for 3x the price of the Optima) bought (used) the more powerful Belles 350 model.  I was so sure this would do the trick, I didn’t check to see if it was returnable.  Well, it wasn’t.  And, sure enough, it didn’t work with my system: still not enough bass and screechy treble.  The 150A actually sounded better.
At this point, I contacted my NuForce technician (Robert Smith) and asked him to give the repairs on my old amps one more modification to see if that would work.  In short, it did, and, after some break-in, my set is sounding better than ever.  (He did a wonderful job!)
I know the Belles is a very highly regarded amp, and class AB is more highly regarded than class D.
Synergy is the important point here. Even the cheap Optima, on my system, sounded better than the other much more renowned brands
With the repaired NuForce, my system is singing again, with better parameters all around: Better bass, better sound staging, much better tonal balance.