Suitable tube preamp for pass labs x250

I'd like to get a tube preamp to use with pass labs x250 power amp. What are your recommendations? I'd like to get a nice, smooth and rich sound from Dynaudio S5.4... I listen to mostly acoustic music, jazz/free jazz with lots of dynamics and rock and roll with plenty of lo fi recordings...

Price bracket would be $4000-$6000
Thanks a lot!