Interesting question, I hope you get some responses.
When I had mine I compared it to my Dynavector P-75 and felt it was pretty comparable. The Dynavector had a bigger soundstage but to be honest, I think it was likely just down to the internal stage not being broken in. This was using a Dynavector Karat 17D2-MKII cart. I felt it was quite a competent phono stage. Hope this helps a bit.
it is very good indeed. I was using a Shelter 901 initially, Plinius did not offer impedance adjustment so I sold it for a Sumiko Blackbird. Even without breaking in the Blackbird, the sound was alive, dynamic, fast, detail, and extended. It was mounted on a VPI SSM, all sit on a GP Audio Monaco.
I don't have anything to compare to here, but I have owned SF Phono 1 SE and ARC PH3 SE, I have heard numerous world class phono stage.
You had no luck with the phono stage in your 8200 MKII? I find mine to be excellent. I'm not sure how much it changed between the two versions, but I will take a hi-res photo of mine and send it to you if you send me one of yours. Did you change anything while upgrading the amp?
Have you compared either the phono in the MKII or the 9200 to any outboard phono stages?
I have read online that someone heard back from Plinius that one may change a pair of resistors on the phono stage board in the 8200 MKII in order to change the impedance loading. By default it is 47k. This may be worth doing in order to use the best cartridge in your price range. Do you folks think that the 0.5mV output of the Shelter 901 is close enough to Plinius' rating of 0.75 (for full output, which I don't need)? I wonder what the 'ideal' loading of that cartridge is. One can also use a resistor in parallel to shunt the signal and change the loading seen by the cartridge. And then there are transformers as well.
I am currently (temporarily) using a relatively cheap Clearaudio Classic Wood on a Wilson Benesch Circle with ACT 2.0 arm, and Apogee Centaur Majors, and the MKII makes me very happy in this system.