Re: About EMG-81, 85 pickups...
I'll word this the best i can.
This is a really good link on how guitar pickups work.
How Stuff Works
That is an explanation of a PASSIVE guitar pickup. The signal is sent to a preamp where it's adjusted (bass, middle, treble knobs etc. on your amp). Then it's powered by a power amp.
The difference between passive pickups and active pickups is that active pickups actually have a build in preamp and are powered usually with a 9v battery. It's like having a built in boost pedal. (active pickups have EXTREMELY high output) As a result, they're very voiced. In an active pickup they can adjust it's tone/e.q. to almost exactly how they want it. Passive pickups are organic, meaning the sound of the guitar when it's unplugged comes through when it's amplified. Different wood types sound different when the guitar is unplugged. Using passive pickups, you have to shape your tone by your guitars wood type, etc. With active pickups, it doesn't really matter because they have such a voice of their own, they sound mostly the same in almost any wood.
Idk about passive EMGs, but to me it doesn't sound like a very good idea.
If your going to use this guitar for ALL metal, then EMGs might be your route. But since they're so high output etc., they SUCK for blues. If you want more versatality, ALWAYS go passive.
hope that helps
-cory