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
An easier upgrade route might be to sell the M30s and buy the M40s.

Few would argue it's not a clear upgrade.
Thanks and sorry, I should have mentioned that I’m stuck with the 30.1s due to space limitations that require me to move the speakers in and out each time I listen. I will buy the 40s in a heartbeat if we ever move!