Try a Darkglass! Rather expensive but the sound is immaculate: http://www.youtube.com/watch?v=gXLr21FZCAE
I mean, SERIOUSLY. That's probably the finest overdrive pedal ever made. :3
Too expensive? You could always try a RAT distortion with the LM308 chip, although that might not be bassy enough for you. I love mine, I run it through an ODB-3 with some EQ and I get a surpisingly bass-heavy, electronics-pushed-to-the-edge tone from it.
It is a guitar pedal, so there's a quite a bit of low end loss, easily EQ'd back in though.
With a little bass boost and some knob tweaking, a clean (ha) RAT sounds a lot like this: http://www.youtube.com/watch?v=kxseYnCaMIk
It's aggro as all get-out, closing in on lo-fi. It's not for everyone, but I wouldn't trade my big box for anything... except maybe a Darkglass or an Animato (0% probability on that one). ;D
If you want more than a RAT, try a Fuzzrocious Rat Tail/Rat King. The Fuzzrocious is basically a souped-up RAT that works wonders on bass and keeps way more lows. I personally don't have one but a lot of people love them- Fuzzrocious are good people and their pedal prices are good for a boutique company, you might want to look into them for some options that aren't so run-of-the-mill. They have tons of options for heavy/grungey bass tones.
Fuzzrocious Grey Stache, a souped-up Big Muff: http://www.youtube.com/watch?v=V3xJdygleEk
Devi Ever makes some great pedals as well. She does quality work and a most of her pedals are right on the $100 mark.
Check out her Black Spider overdrive/distortion mashup: http://www.youtube.com/watch?v=pTd3SJM3fQc
It's a combination pedal and you can dial in some serious WAOHW-WAOHW-WAOHW type blowing-up amp sounds on it.
She even makes a $50 distortion now: http://www.deviever.com/fx/dont-fear-the-noise/
She rawks. :3