i had a rumble 15 - i hated its lack of bass. my basses all sounded like guitars, and i wasn't expecting big boom - just a little bass when playing quietly.
if you really have to have a very small amp, the hartke HD15 is the way to go. it sounds like a bass amp, which mystifies me since the speaker is so small. people here recommended it to me. it's not expensive, either.
but my rumble 40, which i mostly use at "someone sleeping in the next room" volume (sometimes because someone is, indeed, sleeping in the next room). it sound really nice at low volume, and you can get a lot of variety of tone out of it. if you lack the space, you can put stuff on top of it

i have a bottle of vitamins, a supplement, a tuner, an EQ box and a bundle of cables on top of mine right now.
i like the roland micro cube rx. it's heavier than it looks, though. and for less money, i got my rumble 40, which weighs less than the rumble 25 although is a little bigger.