I think a low growl would be more suited for 250hz type of boost, which is your typical low-mids. Don't cut anything, boost a little bit of bass and boost the region around 250hz ( this value could change based upon the unique tonal characteristics of your bass, so do experiment ). Treble, you can leave it flat. I get a good growl going on with this settings with my P-Bass and DR Hi-beams.
For punch, rolling off the tone knob about 75% on my P with bass and treble boost helps alot. Contrary to what others have told me, I found out that a slight tinge of treble helps bring out the definition in the 'punch'.
Twangy, I would use a pick, with treble slightly boosted and mids cranked a little higher. Bass, I would keep it flat. I usually use this settings along with a graceful addition of overdrive on my P to keep the low end clanking and cranking along.
All this purely IMO, on-my-amp,with-my-fingers,on-my-bass and listened-with-my-ears.