Phono Stage, Cartridge, DeGritter...which one first?

Sell the P6. Based  on reviews, the P8 is a significant upgrade from the P6. Forget additional tweaking of the P6.

To be "all in" Rega camp, P8/10 with their Apheta/Aphelion cart. You can continue the madness after that by further upgrading phonostage. By then, you discover the rest of the system is not keeping pace, and wondering if you should jump ship and try another brand table/cart.

Depending on your lp collection, for me the best is to go with a better table, arm, phono stage, cartridge and then worry about a fancy cleaning machine. Cleaning formula like the Walker prelude and a basic cleaning machine will be more than enough.

G

Record cleaning does not have to be that expensive, especially for ultra sonic. Buy a tank off ebay, and spend a bit more for one with separate power supplies for heaters and ultrasonic devices. The tank is essentially disposable, as you spend about $200 for one. Get a Vinyl Stack spinner with the 4 record option. That's about $350 or so. Now the question becomes how to dry the records. Many folks have good results with air drying, and when it comes out of the US that only takes about 15 minutes. Or you can buy something like a Record Doctor V or Nitty Gritty where the wet side of the record faces down and you can vacuum off the excess fluid and put it right in a sleeve. If you do the Record Doctor you are into the system about $800 to $900 for all new pieces. I found a used record Doctor V and paid $180 for whats basically a new looking machine. The results from this basic set up are excellent, I just did some Ella Fitzgerald from the 60's on Verve label and the results were better than what I got on a VPI 16.5 with Audio Intelligent chemicals. 

Damn, I was just gonna buy an isonic but mc talked me out of it. I think I’ll get a Benz micro Lps now. 

$200 all in for motorized ultrasonic.  Distilled water with 30 drops of surfactant does 100% better than any brush/vac method I've ever used.
I'm done scrubbing records. Just US clean before first play used or new.