SDV 3100 HV owners

I don't know how much you want to spend. For what it's worth. I use Jeff Rowland 735 mono-amps with the Jeff Rowland Corus preamp to drive my Monitor Audio PL500 ii speakers. I've heard several combinations with my speakers and prefer Rowland. Unless I come into a significant amount of money, I will never sell my PL500s or Rowland.

When you say "a bit polite and lacking..." how much are we talking about? Is it a small enough thing where maybe tweaks like cable changes could help bring it where you want to be? Or large enough where the Luxman must go?

I've done upgrades on cables and power cords.  I believe the issue is the amp.  After reading a few reviews of the Luxman M10-X (M900u replacement), it appears that it addresses the specific issues I'm not happy with on the current amp.  Again, the challenge is hearing it, hopefully side by side with my amp.  I'm afraid my future involves lifting and transporting heavy metal objects to find out!