It is difficult to recommend an amp without knowing what speakers you have. Normally with a tube system you start with the speakers, make sure they are tube friendly. What I mean by that is they should be fairly easy to drive, somewhere in the area of 88-94 db sensitivity (or efficiency) with a nominal impedence of 8 OHMs or higher. (Tubes do not like an impedance below 8 OHMs, you will get sound but bass will be flabby etc). The reason for this is that tube watts can get expensive, a lower powered amp has less output tubes which can save money and still give you terrific quality.
Different tubes have different sound qualities. The output tube are primarily what people consider. For instance I like the sound of the 300B tube which have a beautiful midrange quality, others like the 6550 which can produce more dynamic range etc. You match the speaker to the tube that is in your amp driving it.
Like buying any stereo you start with speakers, make sure they match your amp, room and musical tastes.
I am not very good at using all the proper terminology but these comments will get you pointed in the right direction.
I hope I have not scared you off
good luck and enjoy