I passed on the Sunn and went a completely different direction - picked up a very nice practice amp. It's an Ibanez SW35. Tilt-back, 35W, 10" speaker, bass, middle, treble, and presence controls, limiter with LED indicator, stereo CD inputs, headphone jack that kills the speaker, line out, effects send and return. Quite a few features...and all for $60 used and in pristine condition! I didn't really need another big watt head (although all the purists would
certainly approve more of my using a Sunn Coliseum head than the Behringer BX4500 I'm using) , but I did need a small, portable practice amp.
If anyone knows what the "Presence" control does, let me know - I can't hear a difference turned one way or the other.
Never mind, I downloaded an owner's manual online and it sez: "Presence is the ultra-high frequency equalizer. It boosts or cuts the level of the 9.4 kHz region in a range of ±15 dB." No wonder I don't hear anything - it's irrelevant for bass, except maybe turning it down if I hear hiss.