I did just that, switch from a passive to a tube pre. I was using a DIY built copy of one of the best current Passives, the Music First Audio Baby Reference. It was truly excellent, neutral, transparent, detailed, but. I felt I was missing some dynamics and changed to a Modwright 36.5 and yes, dynamics were clearly better and the sound was richer. The textures and notes seemed fuller, less dry.
So in my case, I definitely preferred the tubed Pre. The Modwright would be above your price range, maybe not the L100. I agree with EBM, if I was looking for a $1000 tubed pre, you couldn't go wrong with CJ. I used the LS17, I think it was, for a few years, a wonderful unit.