Ron:
Think about the Fourier series necessary to represent a square wave and use that to backtrack bandwidth. At 3kHz. that's like 18KHz of bandwidth for 2 odd harmonics. So, IMHO 20kHz is too low. Slew rate is important.
Some amps choke on high slew rate signals. Slew-rate limiting affects the ability to hear a guitaur pick pluck or the attack of the hammer on a piano.
Tube stuff generally sounds "warm". I used to be an avid FM listener, but not anymore.
Horns can actually sound much louder with a tube amp with a low wattage.