Most significant upgrade

More creative...I'll try. You don't seem to want to upgrade either front end or speakers. Or amp, or cables.
In a situation like that there is nothing that I could recommend. You could call my Audiolab integrated a toy too because it is though a pretty good one.

Jim, what brought the Harbeth to mind? Excellent speakers, but what are you thinking that makes you feel you might want to go in that direction? A very different speaker than the VS - also excellent. I think Inna's comments are a bit overstated (a lot?) but not atypical of the audiogon commentariat. What could be said of your TT is that is more than good enough to show improvements in tonearm and cartridges. But if significance is what you are looking for, it is speakers that will significantly change the sound you have now, though an SS amp would probably be better suited to drive you ML, not an easy load for a tube amp.

Just get an ear cleaning kit from the drug store...trust me.

Hi Jim

I looked at your system and the only thing I'd upgrade if anything was the CDP you have but then the name of your system is Screw Digital so I guess that Cambridge CDP will be there for quite some time getting dusty. I don't see where your system would need any upgrading but that is just me.

Do you have any power conditioners, audiophile outlets etc etc in your system? Are any parts of your system on dedicated lines? Maybe that would be a significant upgrade?

I couldn't find the name of the cartridge your using and you seem satisfied with your table so I'll say upgrade the cartridge.