Re: single or hambucker for neck?
None of my pickups buck ham, but some do cancell hum. I'm thinking they should be called humbuckers instead of hambakers and some of the other versions I've seen here lately.
The vast majority of players use humbuckers for metal. Single coil pickups generally don't have the output and girth of tone that most metal players go for. It's possible but generally not done.
The Livewire for Strat pickups are actually stacked humbuckers with a built in preamp and are only single coil sized. The output of the Hot Live Wires for Strat is right up there with humbucker type pickups and all that output does make them good candidates for hard rock and metal. When I was running the HS-LW set I got some killer metal type tones.
The SD Pickup Booster has a resonance switch and up to 25db worth of clean boost. Those two features combined will go a long way to making a true single coil pickup better suited to metal, at least in output and girth.