Most pickups have a certain volume they operate best at. Some pickups have more high end than others. I wouldn't recommend coming on the Nirvana board and asking what pickups you should get. In fact, you may hate it. Most pickups have a certain peak in the frequencies, meaning they'll either have too much bass, too much midrange, or too much treble for you.
Some pickups have a certian way they feedback and distort.
I would recommend calling, writing, or e-mailing various pickup shops, and requesting a catalog. This is usually free. If you don't want to wait for a catalog, check out the web sites of the big pickup companies. Here's a few links. Rio Grande I would recommend writing every one of these companies or visiting their web sites before buying anything.