Worth it to upgrade to Rega P3?

You may want to tell about your systems. Worth or not may depend on rest of your other systems - phono preamp, amp, and speakers.

My advice is your key words:"I am very happy with it"
Changing something you are 'very happy' with is a BIG MISTAKE!
The vast majority of audio nuts cannot find 'very happy' let alone 'content', or 'resignation'.
Stick with what is making you happy. Really! you have what EVERYONE is looking for. I suggest you hang on to it.

Consider upgrading to a suspension system of isolation.

Go to Machina Dynamica website, then Promethean Springs. Somewhere there is an article on the effects of vibration.

I use 2 sets-one for my amp the other for my CD player.

check out a P-5