Use a pick as consistently as possible and let the bass do the talking. It helps if you have a very woody sounding bass. I find the great big wound strings on a bass interact well with a pick and let you get some very heavy sounds by using all the plastic on metal to your advantage. This allowed me to eliminate the extra preamp nonsense and just plug into the amp and go. When I was looking for sludgey in your face tones, ala Russian Circles or Pelican, I opted for big lazy speakers and started using this gigantic Traynor 2 15 cab from the 70s. I found that straight downpicking through really heavy passages would move so much air you'd have to be catatonic not to feel it.