Welcome on board
I run a Systemdek IIXE, Tabriz, HDC03a cable, Chorus Blue/Goldring 1042 stylus, into a Graham Slee Accession, into a XS3, through Neat Motive SX3s. Naim interconnects and speaker cable throughout.
At that level the TT almost, almost competes with a Mk 1 Hugo DAC that I use for streaming.
I came to this point from a NAIT3 with phono boards. I’ve also extensively tried the inbuilt XS3 stage and a Stageline N on the journey.
By far the largest improvement to my vinyl replay came by adding the GS phono stage.
The 1042 stylus (Gyger profile) on the Chorus Blue was also a big step up. Bump up to a VM5XX cartridge and you have lots of options stylus wise.
I loved my old NAIT, the XS3 was a good improvement, but a 5i I had on loan whilst the NAIT3 was away for a service was also very very good. I’d stick with that amp for the moment.
I am now looking at TT upgrades, but it’s taking a £3k budget to meaningfully improve on the Systemdek at the spec I have.
I actually think you have a nicely balanced system right now. I suspect you would see a nice uplift by looking at cartridge/phono stage upgrades, IMO, and after going this route myself, I’d look at ones above Stageline level. The Stageline is also a bit awkward without a powered Aux socket on your amp, requiring as you note a separate PS. They will serve you through any future deck/amp upgrades. Cartridge/stage compatibility is important here though, and difficult to demo, so a configurable phono stage can help - Vertere, Graham Slee and others have configurable stages that might be worth a listen.
I’ve concentrated on vinyl replay, but really the single most dramatic upgrade I made was my Mk 1 Hugo. For £500 second hand that thing is utterly amazing. For £900 second hand a Qutest would rock too, as would a Naim DAC. Having just looked up the 8200 player though, it seems very well received, so perhaps adding a DAC might not improve it drastically. My Hugo definitely sounds better than my Naim CD5, though I still enjoy listening to both.
I’m not familiar with your speakers, so assuming they are good for the time being. Others might pick up if they’re a weak point
What source do you listen to most? And before I blow £1k of your cash on a new phono stage, what is your budget?