Can’t go wrong with BAT. An "SE" model is preferable (6H30 driver tubes). Is the remote control included?
O.K., this explains it. The VK-23SE preamp has a transformer-coupled output stage. Thus the "SE" designation. Normally, the output stage incorporated capacitors (not claiming to know the technical reasons). Apparently, the transformer-coupling is superior to caps. Whatever it's doing, my VK-33SE sounds like a dream (also transformer-coupled)!