On the Gnex you have to go into settings/sounds/music effects and select Volume+ rather than MusicFX. My wife is in town and she has the Bionic so I can't check it's settings and I don't remember if it has such a setting or not. Good luck with that though.
I do remember from my visit to the dev's website that if you have DSP on your phone you must disable it for Volume+ to work.
yes it does work i have mine set to +13 its about 20% louder at +8 its about 10% louder i use it for the "Complete Alex Jones" radio app when im in the car works great