Where's the volume on your bass? You can be distorting at the bass preamp which would have nothing to do with the amps. I have this Mesa amp that sounds amazing with my Musicman Sub. I can crank the volume on the music man, boost the bass all the way, boost the treble all the way and it sounds good, no matter what. Passive pickup with active electronics. My much hotter, active Warwick, when I plugged in for the first time with my normal settings, (volume cranked, bass boosted 25%) sounded downright terrible. Totally farted out. It sounds fine with these settings on my Genz Benz, but the Mesa just didn't like it. I was completely frustrated until I brought the volume back on the bass, zeroed the preamp, and used the amp eq controls to get my sound. If you're getting distortion at low levels, it's either a piece of crap, or you're doing something wrong. Keep in mind all of the gain stages, from your guitar, to the preamp, to the master volume, and the eq's and filters in between. Also, a single 10 or even a single 12 can often have a hard time with those low frequencies. Looking to a 15 or a 2x10 is worth considering.