Claudio Sanchez and Thomas Erak have some of my favorite guitar tones (quite different though). Both of them say they peg all 3 frequencies on their respective amps. I was wondering if anyone else did this? I have a feeling if I do this on mine it's going to sound like a pile of crap.
An amp with passive controls like most guitar amps do. If you peg the tone controls your just not cutting anything. As you turn em down you dump those freqs to ground. Even with B/M/L pegged it will still have a pretty good midscoop. All you can do is try it.

One side of my stereo signal is run thru a bass amp with active controls. I set my controls to the boost side so they are gonna be running hotter than if the knobs are set at 10 on a passive, sounds fine.