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

Just figure out a budget, get the best cart/table and phonostage. Until you've invested at least $5K-10K+or so, a US cleaner isn't necessary, IMO. Buy good records to start, and you can postpone a US cleaner. I've done this for years, and get away with a $75 Spin Clean.

The proof is hearing  the very same records and playing them on uber systems, and hearing them how they were meant to be-noise free, organic sounding and dynamic as no file or CD can match.

I only buy used LP's, so my saying buy "good" LPs to start is a challenge. That's another thread. 

Just FYI - my current system is a Rega P6 w/ upgraded Groovetracer platter & sub-platter & a Hana SL cart paired with an EAT Petit Glo phono stage.  It's all sounding pretty good but i've recently wondered if a new cart would take it to another level - then I thought about how clean my vinyl was...and so on.  I have clean power with Audience Adept conditioner, so I should be good there.

Vibrato makes a nice affordable RC although the Degritter has caught my eye and ear. 

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.

In this case you have narrowed the question down to where it cannot be answered. This is audio, not philosophy. 

If you're going to clean records, the Walker Enzyme 4 Step is the best, period. But not as huge an improvement as a better phono stage, or cartridge. Unless.... it all depends on which ones and how much, see?

Ahhh.  I understand your point.
Since the Degritter is around $3K, I guess my question would be - in my system listed above, any suggestions on specific improvements staying in that price range? Or go for the US cleaner?