Are future improvements in Amp/PreAmps slowing to a crawl?

@geoffkait 
You quote people I'm certain you've never even read. There's never been much doubt about gravity waves. Einstein clearly laid them out along with their behavior in his General Theory. 
What's more, metaphysics is a legitimate study. If you were at all versed on the matter and how it interfaces with actual science you wouldn't show up to forums and make a complete fool of yourself. 
And what exactly is a "pseudo-meta-physics"? One who feigns skepticism but really buys the BS? Guys like you are the problem with the concept of open mindedness. You think if anybody applies any scrutiny, thinking, or discrimination to a concept they must have a mental disorder. It's ironic you're always trying to shoot down skeptics of your fantasies with accusations of them being mentally defective in some way. Scientific American did a great article a few years back on why nutjobs like you buy into Morphic fields and conspiracy theories. Might not want to read it though. I've got a feeling it'll strike some nerves. That, and it's actual science. 

Shadorne
yep
and that stuff they call music also

have you heard that Benchmark amp ?

Benchmark licensed a device or circuit topology that uses feed forward to reduce distortion when going from class A to B (or was it AB).  I have not heard one (yet) but people I trust really like it.  It's on my list.

people who think innovation has stopped should read the thread "Class D is Like Candy"

dunno if it has slowed down or not - but it has not stopped

Over the years I've owned some of the finest sounding amplifiers ever made. I'm positive that a few would still be competitive today.  I returned to the hobby this year after a 9 year absence - starting with a clean palette. I started to research the current SOTA in amps and preamps with absolutely NO interest in class D amplifiers. I never heard one that came close to reproducing music realistically among their other problems.

 I set a budget of $8k for amplification hoping I would find a mint used set of monoblocks in that price range. I kept hearing great things about the Bel Canto 600M's and even though I was dead-set against class D, I took a trip to hear them. To my total surprise they sounded great - no hint of that sterile class D sound - no lack of musicality and detail. In fact, inner detail retrieval is outstanding. I purchased a pair. 

No, they aren't perfect, but if you write off class D amplifiers based on the examples of 5 years ago, you would be making a mistake. I have a very musical, detailed presentation with good slam and attack. There are other positives. The cost compared to my budget was far less and a bargain for performance at this level. I'm also happy that they run cool. My previous monoblocks - Sierra Audio Denali - required me to run the A/C in the winter in order to keep the listening room comfortable. 

I know there are other great options at the budget I set. I listened to many before making my decision. It came down to buying a great set of amps for only $3k (dealer demos) that compete with much higher priced amps.

Class D has come a long way.

To answer the thread question...
Nelson Pass is right (about Nelson Pass)

Pass:

Oh, I want perfection, all right, but I'm secure in the knowledge that I won't achieve it.

Some designers give up looking for perfection. Its extremely difficult even with state of the art devices. This is why there is a mindset that you just have to take the pros and cons of various components and make the best combination that gives you the "sound" you're looking for.That seems to be the norm.