Here is my
main thread on the SA200. It is the best all-tube head that I have used for electric bass, and truly a thing of beauty. But yes, it is overkill (weight-wise and volume-wise) for double bass.
Tom.
P.S.
The new Sadowsky cabs are really something special, too, IME/IMHO, and the SA210 might make for a killer upright box.