This is a great thread, i have just registered, so my humble gratitude to everyone who posts here, thank you for sharing your exp. and knowledge.
i know this is kind of old, so i'll sum up:
for ultra low power its
the zvex nano-head, and the emerysound microbaby, when we are talking no speaker/cab.
i think this is the big one - a great tube amp but just the head, maybe plug it into a laptop, or a tape recorder or something like that i'm thinking.
I guess i have this question, can you get the output from a low watt tube power amp into like an instrument preamp, or even a soundcard input (a proper soundcard mind you, eg. m-audio or focusrite etc. there are tons) so you could record that sound.
put in another way, can you modify a small amp to have a line output even for headphones.