Tonearm recommendation for Dynavector DV-20X cartridge.

Google Jelco with On the fly VTA.

You have a number of choices in your budget range.  Keep your eyes peeled for a Micro Seiki MA-505, Graham 1.5, 2.0 or 2.2.  They all have VTA on the fly and are truly superior matches for the Sota & DV combo.  You would definitely get the best out of the 20X with any one of them.

Grace, Ortofon and DV arms are also really good, but lack VTA OTF; a DV 505 would probably stretch your budget a fair amount.  SME is another choice, but can be a pain to mount on the Sapphire.

Tri-Planar and JMW can be made to fit, but require modifications to both plinth and body.  Tri-Planar would probably also stretch the budget.

A last alternative could be a Magnepan Unitrac I.  Long since discontinued and not readily repairable if you have a failure, but a truly excellent performer that can be found at a reasonable price.

FWIW, my picks of all the above would be the MA-505 or 1.5.  Solid performers at attractive prices that have the ability to extract the very best out of the very best.

Good hunting and happy listening!