I'm currently running a single 1x15 cabinet with a Bugera 1960 tube amp, which is rated to around 100w/150w. This is really really loud when it's run into heavy breakup, but at a volume where the bass is still reasonably clean, it just isn't loud enough for what I'm trying to do. My question is, how much louder can I expect my rig to be if I put in another matching 1x15 cab? These are cabs I've built myself, so it might be difficult for you guys to know what I'm trying to work with here, so all I can say is that they're quite large, ported, and bass heavy cabs, with some efficiency sacrificed for a deep rumble. On a side note, I would recommend the Bugera to anyone who wants a nice, reasonably inexpensive all tube rig, but doesn't need bring buildings down with volume. The tone is fantastic, it's got a really lovely midrange with a nice vintagey muted high, and plenty of low end. Quite flexible as far as different tones are concerned too, you can get a lot out of it by mixing the channels.