Most significant upgrade

If you ask me I would get that Rega toy out of the system and bring Nottingham Spacedeck/Spacearm in. As for the cartridge, there are many choices, it depends.

Straightforward but usually polite enough. Sometimes oversized too; it happens.

Yes, a toy. As I suggested, try Nottingham or one of those German tables - Acoustic Signature, Acoustic Solid etc. and you will agree. Yes, of course, it'll cost some money.
Well, at the very least you could upgrade to P7.
Speaking financially, serious analog starts at about $3000 new for table/arm. Plus cartridge.
You asked for significant upgarde, that's my opinion. You like your speakers so I said nothing about the possibility of upgrading them.

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.

Jimbojrjb, you know that I am right. Glad I could help. And I did it the way we do things in Texas. Not exactly French style, true.

If you beg for mercy she might not or at least do it in style.