Good Matching Preamp with Pass Labs X350

I am using Sphnix Project 8 preamp with Pass Labs X350 power amp, but miss the warm and harmonically rich sound generated by my previous tube gear. I am thinking of replacing the preamp with a tube preamp. Any suggestion that can bring back the previous lovely sound? Audio Note M3, Conrad Johnson LS17? Or any others? I am afraid of Hovalnd HP100, which looks marvellous but the some 23-steps volumne control gives too little flexibility. Thanks.

Hififan