The bass filter in the Q-Wah is okay, but it doesn't really get very wubby or very wet sounding. I found the ModFilter gives a much thicker bass envelope sound.
I use an Agent 00Funk right now, and the H9 just can't emulate some of those sounds. Or even like an old DOD FX25 – the H9 just can't get that greasy, deep, or squishy sound.