Well, there are a lot of clean parts in Stevens music so I don't think the D-Activator is necessarily the best choice for a bridge humbucker as the cleans are not the greatest.
I'd much rather go for something more allround like the AirZone, Norton, Transition, Breed or Breed Neck (yes it works great in the bridge!). Especially the AZ which for a big-sounding, crunchy humbucker has exceptional cleans and it splits beautifully too. If you then need to pile on the gain, say via a boost pedal or something, youre rewarded with a huge, fat tone.
As for the middle and neck:
For more power: Satch Track in the neck (the only railbucker Ive ever really liked. In fact, I love it. Fat, punchy and clear). Injector Neck in the middle.
For more of a "vintage" tone: Heavy Blues 2 in the neck, Area 67 in the middle.