My profound ignorance regarding tubes is becoming increasingly apparent to me.
No call for embarrasment at all. That's pretty much where most of us started. If you've read the responses so far, then at least you know SOMETHING. Besides, with much of the plug-and-play, auto-biasing circuits designed into most headphone amps, preamps, and many power amps, you really don't need to get much beyond Big Bird and Ernie to enjoy what the potential of tubes are in audio gear. Just use the two ears you've got and make your own decisions. Who knows, you may prefer SS...stranger things have happened. Seriously, there's plenty of folks who go that direction. For me tubes, at their best, have an ease and a natural, lifelike presence that SS can only strive for but never quite reaches the same mark. Yet I've heard SS amps I've really enjoyed for what they have to offer that tubes cannot. Or perhaps a hybrid solution that utilizes both tube and SS technology. Go out there and listen. Pick your poison and enjoy the music. Another option is that many of the head amps are available on a short trial period (7-30 days usually) from either manufacturers or dealers. You may be able to get a few and compare in the comfort of your own home. The only drawback there is that the sound may change, either subtley or profoundly, as the circuits burn in with use. Tubes also change after an initial burn-in. So you may be missing out on some aspect of performance without a burn-in period. If you are in a vast metropolis, just find a local dealer who might have some examples and bring your cans and your music. A local audio club may be another option. Or plead here on this forum for other members in your area who may allow you to come listen to their gear. I'd bet you'd find one or two who might be willing, since you are an established member.
Have fun!
Marco