As you can readily tell from the responses, many amps have easily identifiable characteristics usually refered to as a "sound". If your priorities include an effort to approach a natural quality of sound, then I suggest that you listen extensively to acoustic instruments and voices in performance and then use that perceived sound quality as your standard. If your priority is to just have your system sound pleasing to YOUR ears with no desire to come close to the original sonic characteristics, then simply purchase what sounds good to you. Tubes are still well-liked by many I think because, generally speaking, they roll-off the top and fatten the bottom. This may make certain stridently rendered digital recordings more attractive and enjoyable to listen to. It should be pointed out that ss gear can be designed to closely replicate the qualities of tube equipment. The converse is less easy to achieve and to a large extent, not do-able. In any case, given the variables of equipment interactive relationships, individual levels of experience and sensitivities, and particularly, TASTE, there is little assurance that anyone's opinion will be reliable for you. I can assure you that if you prefer tube amplification, you should be prepared for changes of sonic attributes with every tube change. It's interesting that "audiophiles" will often spend thousands to make subtle changes in system characteristics. I.e., tonal modifications (sometimes, in effect, very expensive tone controls), Yet, the often shunned simple tone control will sometimes offer a sufficient solution. This leads me to a heretical suggestion; in your search you might also consider trying a pre-amp which offers you the option of some tone controls. You might be surprised at how effective one can be. A very nice, moderately priced one has been made by Musical Fidelity in the past. Of course, there are other options which don't involve hardware changes. I'm sure that there would also be many suggestions for that too:
