id say they are fine if you set your gains with it on max...i miss having one, its nice being able to turn the bass way down with just the turn of a knob...
for your amp its a bass gain knob. I use mine and love it.Gives so much control for me cause some cd's are mp3's and some are original. What i suggest though is to set the gain with the bass knob out and then put it in.
when the bass knob is at max it is where you set your gain on the amp, thus if you set the gains on half and bass knob at half way then it = 1/4 gains up on the amp.