Myriad_Rocker said:
I started thinking about this today. Would this present a problem?
The question is not "would it" so much as "does it." How can we tell youif it presents a problem? Only you can tell us if it does or not.
Overall, I wouldn't worry about it. The cab doesn't need to be touching a surface (like the floor) to vibrate it. If you crank that puppy up loud enough to be heard through the wall in the bedroom next door, you are therefore vibrating the wall between the rooms. That wall vibration is what the person next door is actually hearing. If you're going to worry about the floor, then you need to worry about the walls and ceiling as well - for they are also going to vibrate and add their own resonances - and you'll drive yourself crazy thinking about it.
I will say, though, that I'd as a general rule, take your cab off the floor at least 6", preferabley at least a foot. Not necessarily for the vibrations issue, but just to tighten up the sound of the cab. Rare is the 1-by, 2-by or 4-by (or consumer playback speaker, FTM) that doesn't sound better when brought up off the floor, IMHO. And, if you like, you can throw a little isolation padding in the mix.
Of course, you'e still going to vibrate the entire house, but at least you'll have minimized them somewhat and gotten a better-sounding amp in the bargain. But beyond that, unless you want to install a floating floor system (not that hard, actually, but also not much of a help in a 2nd floor bedroom), don't worry about it until it's time to build your own studio.
G.