A 6W amp with an efficient speaker can easily be truly louder than a 30W amp with an inefficient one. Louder than a 100W one with an inefficient speaker, for that matter. Amp and cab vendors seldom tell us anything about speaker sensitivity, you can only find that from the "driver" manufacturers, and even then the ratings aren't all done to a single uniform standard.
"A cheerful heart is good medicine."
I've got a POD XT Live plugged into my Valve Junior and the volume control takes it down to almost nothing with very little effect on tone. Perfect for low volume applications.
Dean Icon PZ
Line 6 Variax 700
Dean 79 ML (silverBurst) Dean 79 ML Arctic White
Dean V-Wing Dove
Wampler SuperPlextortion - Skreddy Lunar Module
Peavey Transtube 110 EFX - Vox DA20 - Valve Jr Head/Cab
Phonic 620 Power Pod PA
Line 6 Pod HD
H2O Chorus/Echo
I've never played through one of those before but I just saw one at a pawn shop for cheap and it looked interesting. My friend has one of those Maudio black box things (not sure if thats right) and its pretty cool for recording and effects.
Take a look at the Blackheart killer ant. Less then 1w and has some really decent tone.