Re: Boss Katana or Tube Amp or else?
The problem with tube amps is that they're in general heavy and loud. Too loud to comfortably use in an apartment, for instance, unless they come with an attenuator or you buy one separately.
As for what works best with the stick - I really couldn't tell you for sure. I only have experience putting guitars through guitar amps! But I imagine your best bet would be something that sounds good clean and comes with a nice sounding reverb - the Stick benefits a lot from the latter!
Typical guitar amps unfortunately only have one channel, which doesn't really let you take full advantage of the fact that the two halves of the stick are separate. I imagine something like a stereo keyboard amp, or a PA speaker, would be better suited, but I know even less about those!
If you're asking about buying a guitar amp for your guitar, if you just wanna practice you really can't go wrong with the Katana. I've heard nothing but good things about it, and it sounded great in the demos I've checked out. However... why are you asking in the Stickist forum?