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

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

The Audiomods Series V is $1000 with the micrometer (not sure I need or even want that) and a few dollars less without.
Maybe the Audiomods arm would be a nice match for my cartridge I don`t know.

 A Delrin platter for $350 can be added in for added mods too. 

So at this point I`m looking at another $1250-1350 to be added to the P5.

It`s kinda looking like a late model P9 or an RP8 might be a better deal after all is said and done ?? 

I'm not sure you will notice as much of a difference moving up the Rega line as going to a heavy platter design. Maybe just stick with what you have unless you are finding a particular parameter lacking.