IMHO, demoing anything, even cables, in an unfamiliar room/setup can be challenging at best. I have purchased speakers that sounded entirely different when I've gotten them setup in my room. Even if the dealer is using the same gear and cables as you, his room may be different.
I'm not saying that you can't get some kind of idea. However, for me, when demoing, I only know whether I like the sound or I don't like the sound. In either event, I don't know that I could pick out which component to praise or blame for the overall sound. Good luck with that though.
I own a VPI Prime and use a Allnic H1201 phono stage, though I'm sure that is where the similarities between our systems ends. I have owned the Dynavector XX-2 mk II, and that is a good cartridge that mates well with VPI tables. I am currently running a Transfiguration Phoenix S cartridge, which while not as dynamic as the Dynavector, sounds a bit more natural to me. I also own a Ortofon Cadenza Bronze, which is a bit warmer than either of the above.
I have not heard either the Soundsmith Paua or ART 9 carts, but I did own a couple of ZYX carts a few years back. The UNIverse II, or a 4D would also make some great music (X version).
There are many great choices, and it can be overwhelming. I don't know that there is one clear cut answer. You may even find that different carts strengths and weakness', may mean that some work better or worse with different types of music. One that has a pure mid-range, and work wonderful on female vocals, may not have the dynamics of another cartridge that may work better for rock or orchestral music.
Sometimes the more research you do, the more difficult/confusing the choice becomes.
Happy hunting,
John