I've used an EHX Bass Preacher for a while now, mainly for acoustic numbers as it seems to help get through the jangly mush of the acoustic guitars and also seems to warm the tone up a little, makes the bass sound more intimate. It is quite brutal at cutting the highs but for those numbers, it doesn't matter so much, I don't really use it for anything else. And they are pretty cheap, £75-85 at the moment. I've always found EHX gear a bit hit and miss but you do get the odd gem.