Signal tube versus power tube, sound impact?

What kind of amps are you running? 16 power tubes? WAG, but sounds like some Primalunas I've seen, but not heard. What kind of 'signal' tubes are you running? What kind of pre-amp are you running, with what kind of 'signal tubes?

Specificity might get you a better quality of response. 

Power tubes first, small tubes to fine tune. JJ power tubes are OK if you like them. I use their E34L's in a small amp in preference to some other excellent tubes. Power tube selection can make a big difference in the sound so the first thing you need to do is try to define what sound you want to hear. While tubes do interact with your amp to get this sound power tubes do have a intrinsic sonic signature (as do small tubes). FWIW new production tubes are generally good, NOS power tubes are exceptionally hard to find and very expensive.