So many preamps, so little time

I am trying to move up the tube audio food chain having left solid state recently (after listening to tubes I can never go back). Since then I have gone from ultra-linear tube amps to a used pair of Cary 805AE (300b) monoblocks (very happy!). I still have a Primaluna Prolouge 3 tube preamp; I rolled a pair NOS Radiotechniques (French military 1955)and a pair of Pope Holland (NOS 1959) replacing the stock Chineese 12AX7 and 12AU7 (which have really opened up that little preamp).

My interconnects are Acoustic Zen and speaker cables are Red Dawns (Silver)connected to a pair of Vienna Acoustic Concert Grands (sensitivity 91db). I have a Cary 300/303 CD player, and PS Audio line regenerator.

My sound room is small (12 x 12)so my listening is mostly direct energy from the speakers. Still, I enjoy a wonderful soundstage with much of the benefits that tubes provide.

I would appreciate your recommendations on a preamp upgrade. I have tried bypassing the preamp altogether but have decided not to go down that road. I expect to be looking in the used market for something.

Is it a waste of money to buy a balanced-preamp with an un-balanced system? I find reviews aren't any help (every preamp out there is "always the best"). What do you guys like? Any input would be appreciated.