Here's 6Moons blazing trails in the tiny-powered tube underground. Of course, being 6Moons, the reviews are encyclopedic in depth and length. So here's the Cliffs Notes. First up, the $800 Almarro A205A with all of 5 watts (but they're big watts!):

As others are finding out, the little EL84-equipped Almarro A205A MkII is one heck of a good little amplifier and one that I highly recommend to low-powered valve lovers everywhere.

Next up is the $1995 Music Reference RM-10 with 35 watts of EL84 tube goodness:

No flash, no glitz, no wonky liberties, no silly excess. This is an amp backed by a designer with a test bench who knows how to use it. He wouldn't spring something on an unsuspecting public whose every measurable performance aspect couldn't be justified.

Finally, the $4200 SilverTone Audio Model 3.2 rocking micro-powered 300B tubes:

Based on what I believe attracts most prospective 300B enthusiasts to this tube in the first place, the SilverTone Model 3.2 is a very welcome addition to the genre and one that doesn't suffer the usual excuses made for bass weight or extension.

Read the reviews for all the goods.

Almarro Audio
Music Reference
SilverTone Audio