Mod my Rega P5 OR...time to move on ??

Substantial improvement is possible without an unnecessarily large outlay.

"I put 3 Cardas blocks under my Rega which helped quite a bit. There is no need to "move on".   Lots of money with only a bit of additional performance."
Did you use the Rega wall mount bracket ? I use one but it`s not on the wall. I have mine attached to the center brace of my rack. 
 
"Substantial improvement is possible without an unnecessarily large outlay"
Details Please...  

It sounds like you have the upgrade bug, and typically a heavy platter table will give you net gains across the board if well designed. Selling your Rega and finding, for example a used heavy Systemdek would be a reliable pathway, among others of similar design.  Cartridge tonearm compatibility is a factor also. I would stay away from anything "vintage" as it's not necessary and there can be downsides. There are high value new tables available also. The better tables are more highly resolving and better reveal layering and transient fidelity not to mention frequency response  and an overall more even, sophisticated sound. Your ZYX is a very  fine cart also. 

If you get an Audiomods arm as an upgrade (which it will surely be), you can keep it if you later decide to move on from Rega (keep the Rega arm to remount). If you DO go with a new VPI table, know that they now come with non-interchangeable arms, of which you may or may not like. The Audiomods and VPI arms are VERY different from one another.

@bdp24 - i would be very interested in knowing how the arms differ.

Do they offer different compliance?

Is their compliance matched to a given TT model?

I've been more focused on their plinth design than their arms to date

Thanks for any info