Need More Power--Alternator Questions

[OG lil E]

I've been planning and scheming to get airbags on my truck. Alot I've read about says that the compressors pull quite a bit of power. I've noticed that when I drive my truck with the headlights on and heater going, when I stop at a light, everything dims. I plan on adding an aftermarket stereo as well as compressors for airbags, so a bigger alternator is a must have. I was wondering if a one wire is the way to go, or should I just buy a bigger alternator that hooks up like a stocker? I put a one wire in my '62 Buick, but that has been 6 years ago and I can't remember how my mechanic told me to wire it up. Our trucks are internally regulated, right? Also, has anybody had any experience buying alternators from mail order or Ebay? Mail order prices seem to be the best buy, but are they? Lots of questions, I know, and as always, any help is appreciated! E