If you ever really want to mess with the sound, try adding even more batteries. Most active EMGs can tolerate up to 45V (though I would be weary of what your rig can handle on input) at battery-capable current levels, so you can go nuts and add more batteries.
I did it with a bass years ago, and the difference is sound is really drastic- way more so than I thought there would be. It didn't sound any different to me between 9V and 18V, but after the jump to 45V the bass sounded like you were plucking granite strings with a dull chainsaw. It was insane. It sounded almost like a Rickenbacker.
That is to say...it sounded horrible. EMGs do not belong in basses, in my opinion!