Amp with best bass control

Everything you mentioned including 'lowest' can be attributed to the Acoustat TNT200. Especially in mono. Every time I think I'm experiencing the limitations of these amps, they surprise the hell out of me. They are brutally honest from the bottom, up. Mind you, mine are rebuilt/upgraded by Roy Esposito in Florida.

Best control per dollar? While I'm reluctant to suggest any "best" in audio (too many variables), for their current used prices I agree with Bdgregory, any of the Electron Kinetics amps - 2, 4, 7, 400 - are still hard to beat. Iverson knew what control meant.

In answer to your question; IME: most, but not all Krells.

When I bought my Krell 300cx I had auditioned the Sim amp as well. There are 2 reasons I went with the Krell. The speaker terminals are way too close for my liking. If you put a set of spades on them the sides would be very close to touching & it frightened me. We are talking close. 2nd reason is I believe it is on all the time. I dont mind stand-by, but on, I didn't like. No switch on the front.
The Simaudio W5 amp had great bass and sound quality when I auditioned it. It is a very good product.

Isn't Class A supposed to be superior for bass control? Wyred 4 Sound is one example.