Tube amps for quiet play
Is a tube amp too loud for use in the typical home? There's a tradeoff, depending on the tone you want.
If you want great-sounding overdrive at conversational levels (say, as loud as a TV set on a typical evening at home), then any tube amp rated at more than about one watt is going to be too loud for you. The tradeoff is that an amp that small isn't going to give you much headroom at all - your clean tones will be very quiet.
Master volume amps can be set for very low volumes, but then all of the distortion is coming from the preamp tubes. The power tubes and speakers simply don't produce any significant distortion at very low volumes - the amp can't "breathe"...
So if your goal is great tone at conversational levels, or if you live in an apartment and your neighbors value being able to hold their own conversations without raising their voices, then any tube amp is going to be too loud for you. In that case, I'd strongly recommend that you consider a modelling amp or (preferrably) one of Fender's Cyber amps.
The flip side of the question is: "Does a particular tube amp sound good at low volumes?" In other words, if you're willing to play with a very clean tone at conversational volumes, can you find an amp that will have a satisfying tone?
In the case of the Vibro-King, I'd say yes. It has a very rich, complex tone (aided by the reverb) at low volumes. You can even get a bit of distortion in the tone by running the tone controls close to zero and the volume above 4 or 5. But it's not the same sound you'll get when you open up the amp and play it loud.
Remember... tube amps are designed to sound their best at performance volumes. Unless you live in a theatre, think twice before buying a tube amp strictly for home use.