One of my tts is a VPI Classic 3 Sig SE.
First, the JMW arm is not a 3D arm. If your Classic 3 isn’t a Sig, you’ll need a HRX pulley for the ADS. Best sound then is with 3 belts.The VPIs, sadly have a long history of manufacturing issues, one being S2P distance being off. If other owners haven’t noticed this, I’ve tried to make them aware. The Sig feet will not be a significant upgrade over what you currently have. (A well thought out platform will serve you better for any tt you have/want). Having said that, I’m currently using Stillpoints SS Ultras. Still had to modify the motor cover plate on the underside for these feet to sit equally square. A good mat will be very beneficial. I use two MyMats. I found the dual pivot upgrade to be significant but since it was an afterthought, I’m not sure it will outperform more thoughtfully designed uni- pivot arms.
I have to say, with all of the thought into my VPI, it sounds very good now with my Sussurro MkII. It was a struggle to get there though.