Of course this is not always the case and different amps and pre amp will make a monkey out of the following statements, but here goes: IMHO the tubed pres add air and dimension around intruments, widen and deepen the soundtage. Paired with a good SS amp that is quick gives punch, dynamics and bass extension. An all tube system will sound warm and mellow but may lack punch for driving jazz and rock and intense classical climax and that may be just fine for you. I think in general a SS pre with a tube amp may sound clear and clean but will sound constrained and will leave you unimpressed with the bass. In general my preferences would be 1) tube pre, SS amp 2)Tube amp and pre and 3) SS pre, tube amp. All that being said your source componenets will also make a big difference in overall sound characteristic. If you can listen to these combos in your listening room and go with what sounds good to you. That's really all that matters.
