Is there a point of diminished returns with amps and Harbeth 30.1s?


I’m currently using Herron M1As with my 30.1s and I’ve upgraded the rest of my system (Aries/Fatboy/SUT/DL103r and Lamm pre and phono) and each upgrade has been VERY satisfying. So is it going to be worth spending $5000 or so on the used market to upgrade the Herrons? Any thoughts as to whether I’ve reached the apex of amp/speaker performace for the M30.1s?
dhcod
I’ve never really understand the usefulness of blind tests. Do people actually know what they prefer in a short listening A-B session? It takes me a week of listening to determine if I like the sound of a component, unless it’s truly horrible or completely mismatched. I’ve fallen in love with many things upon first listen…. only to want to hang myself for a stupid purchase a week later. 
The amplifier thread on HUG (!) is interesting if only for the remarkably *wide* range of amps that owners are using with Harbeths.

I think the company went over the edge in the issuing first of the Anniversary series and then the XD series, both of which entailed very large price increases, one on top of the other.  I'm just glad I snagged my (regular) 40.2's when I did.
I had listened to a couple of Harbeth models some time back, and my impression is that they are definitely in the warm and fuzzy camp. It is such a subjective thing, and different people have widely varying preferences for sure. They do play women singer voices very nicely.  But to me I prefer a bit more clarity and impact in the sound of my system.
I’ve never really understand the usefulness of blind tests. Do people actually know what they prefer in a short listening A-B session? 


I agree that this is potentially problematic, but to be fair, such tests are not about preferences, but differences. In other words, can the listener simply and consistently distinguish between components, irrespective of which they may prefer.

But while the science suggests that humans have very short auditory memory, I'm with you on the value of listening to longer stretches of music in order to make confident judgments about differences in components.
@whipsaw ,

"In other words, can the listener simply and consistently distinguish between components, irrespective of which they may prefer."


This seems to be the main problem the anti blind listening test brigade have.

No one has regularly managed to distinguish sonic differences between amps, cables and digital sources.

Therein lies their problem.