Tried any of Roger Mayer's stuff? How about Michael Fuller's Fulltone
stuff?

I have the Fulltone Bass Drive for use with my SWR Workingmans-15. I think
it's great. It doesn't suck the low end out. You can go to searing
tube-ish distortion. But best of all, you can also go from mild warmth to
slight crunch without destroying your sound. And you can also defeat it's
compression, so it's versatile for a stomp and sounds great.

Doug