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

If you were considering any of these changes, which one would make the most immediate improvement without narrowing it down to a specific phono stage or cartridge...interested in some feedback from the analog folks here.
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do you have spacers under the P6 tonearm to level and optimize the VTA of the Hana cartridge? 
“absolute cleanliness “ does not exist in a NASA cleanroom, but who knows...i could be wrong. post up that SEM photo for us in the system photos.....

It really bothers me when these Rega TT get upgraded so much beyond upgrading the carts. You have a really good setup. I wish you would have sold and traded up to the P8 and the Apheta3 cart. You would be done for a long time. You have a really versatile phono stage due to it can dial in almost any cart on the fly. I agree with MC 100% on the cleaning. You don’t wash your car and then dry it with a towel laying on the ground in the dirt. Buy the Ania pro “not the Ania” if you will keep the P6 for a while or even better the Apheta3 cart if you will go to the P8/P10 in the future. Keep a lookout for the Herron phono stage. Bottom line buy the Apheta3 cart first then work on the rest. 
I forgot to support my local Hifi store in the Chicagoland area. carry Rega, EAT, and Kirmus US cleaners. They also take trade ins. 
I have personally demoed all of this. I am still trying to decide between VPI and Rega. 
I get a chuckle from people who insult the intelligence of anyone who spends money differently that they do. Pretty comical, really.

If you are serious at all about vinyl, you really do need a cleaning system. An inexpensive vac cleaner is well worth the outlay. That's where I would start. Your current vinyl rig will thank you.

That said, and since you asked about it, I'll comment on the Degritter. I  used a Nitty Gritty vac for a few years and then a lower-end Clearaudio Matrix vacuum for another decade. Both did the job well but they were a hassle to use, so I ended up cleaning LPs a lot less often than I should have. Two months ago I broke down and bought a Degritter. I think it is a fantastic piece of gear. I've already cleaned more records than in the previous 5 years combined. I keep it in a walk-in closet so I don't hear it, slip in an LP and go listen to some music. In under 10 minutes, voila, the LP is clean and dry. And every record sounds great--better than all my careful scrubbing and vacuuming ever produced. Expensive? You bet, but worth every penny to me. YMMV, but I would not think you idiotic if it does.