VPI upgrade?

You can get the Prime 21 with a gimballed arm installed at no extra cost.  The bass response with the gimballed arm is amazing!.  But if you want to change cartridges, you are better off with unipivot.  You can get a separate arm with unipivot and mount a second cartridge on it (perhaps a mono) and make an easy swap.

I got a used Prime about a year ago. Amazing TT. I went with a Hana ML cart. 

I have a used Prime Signature in Rosewood with JMW 3-D printed uni-pivot arm. J.R. Bosclair of Wally Tools fame set it up with the second pivot so it was done right. It has also been calibrated by him for the Soundsmith Paua but the settings should still be correct for any Soundsmith of similar weight. It would cost you a considerable amount of $ to have this set up done. Pricing is in your ball park. Please message me if interested.

Look for a used Superscoutmaster......better than almost anything else.

All of the information and expertise is greatly appreciated. Please remember that my budget is $3,500. Happy to buy used!

Perhaps, I'm dreaming to find a significant improvement.

I looked at the Pure Fidelity website and realized it's an $8K suggestion...They look like works of art.