Are you using it in dry mode? In stock form, dry mode isn't very useable as it produces a large volume boost but this mod can change that: [url="http://basschat.co.uk/topic/112212-bass-big-muff-volume-and-feedback-mods/"]http://basschat.co.uk/topic/112212-bass-big-muff-volume-and-feedback-mods/[/url]
I use it in dry mode with the aforementioned mod, but also run a mild mid-boosting overdrive in front of it and have no problems cutting through. I use the Catalinbread SFT for this at the moment, but I've also had good results with a modded Bad Monkey and Xotic BB Preamp.
This way you can layer your dirt - clean, mild OD, and OD + Fuzz!