preamp suggestions

Any suggestions on an upgrade for my Superphon REV II Basic preamp?I'd like to maybe try a tube pre or find one with a single volume pot but I'm not sure I can find anything that sounds as good for under a $1000.I'm in the process of switching to monoblocks from my Adcom-555 and have Martin Logan SL3's.
Conrad-Johnson PV-11
or PV12 or PV9a

all excellent preamps for your system.
Classe CP50 would be my suggestion.