For whats its worth I use a Boss HM-2 and a V-Stack pedal. Both provide loads of bass with the option for overdrive or outright fuzz. These are typically guitar pedals but the bassist from Godflesh used to use the HM-2 on a low gain setting. I didn't know that when I started using one andIi set mine up a bit different. I happened into an early version V-Stack at a pawn shop $20 and without the LED light. I was jamming with a friend tuned F# standard and we decided to try it to help tighten up the low end. Actually sounded good so i stuck with it. You can chase for you tone and literally spend hundreds upon hundreds of dollars on pedals trying to find one you like. Go to your local pawn shop or music store and try every damn distortion or fuzz they have. You might end up spending less and obtaining a tone that is equal to some of the boutique pedals your asking about.