Analog Upgrade - Where to start?

You have a truly fabulous deck. I would agree with the other posters that you should focus 100% on phono stage for upgrade, even though the Stellar was probably a recent purchase for you.

I’m partial to the VAC tube MM stages. Then add a good external SUT (Bob’s Devices Sky, EAR, etc), and you will never ever again feel your music is lacking an iota of: body, soul, musicality. There was a VAC Standard preamp with their excellent onboard 3-tube phono stage for sale here at about $2K, I believe (I have no association to the seller). I would get that JUST for the phono stage, even bypassing its line stage if you find your current one better. Then add a better external SUT. Or you could start with a nice warm fleshy sounding SUT (Bob’s Devices Sky) and add that to your Stella and see how you like that to start!

As you see, us audiophiles don’t have very strong opinions on this stuff lol. From here, the only way to add clarity to your particular situation will be to try something. Maybe you’ll fall into the camp of Raul and friends, who like clean SS phono stages and fast, clean, neutral, does-everything-well cartridges like Ortofon A90 or Van Den Hul Colibri - it’s very fine sounding gear; nothing wrong with that! Or maybe you’ll swoon to fat sounding tube phono stages, full bodied SUTs, and cartridges with softer-sounding-than-neodymium magnets e.g. Koetsu (as I do, most of the time). Or maybe you’ll have the most fun mixing and match from both sides! Only you can answer now.

I think everyone’s impressed by your table & arms, so at least that hasn’t come under the gun (yet), lol. And personally I’d love to try a Dynavector XV-1s (alnico magnets, etc). I’ll be shocked if that ends up being the weak link, unless it’s worn.