If you're considering humbuckers rather than single coil PUs, I can highly recommend the Wilkinson PAFs. They're inexpensive, and produce a very pleasant sound that is suitable for everything from clean to high gain, with clear bass and treble response (so it doesn't get muddy, like some humbuckers). Also, they're created from the original PAF design by Seth Lover, so it's the closest you can get to the 'original' humbucker sound.
Absolutely. The only downside is that it's a lot of work to mod these PUs if you want to use them split-coil. But you'd be mad to do that to PAFs in the first place.