I had one of these for a while and enjoyed it. It's a solid-built little piece that delivers a clean, tube sound. I had the 1st upgrade, but as @noromance said, the biggest difference is going to be upgrading those stock 12ax7 tubes. I used a pair of Amperex Bugle Boys and they really opened up the sound.
Also, Jolida has great customer service from their HQ in Maryland.
Also, Jolida has great customer service from their HQ in Maryland.