I've heard the overdrives are pretty good. Though as another option for overdrive, there are a few basschatters selling a Marshall Jackhammer pedal for (I think) £30. Actually very good on bass! And they have bass, treble, and adjustable mid contour knobs on them. Sounds great as a mild overdrive, and if you've got a blend pedal to retain your clean low end, it also sounds amazing at high gain settings.