When deciding on pickups, I will usually play a guitar through my amp for many hours playing all sorts of different stuff, taking note of how it responds when clean, playing crunchy, fully distorted, etc. Then I will make a mental checklist of the things I want to try to eliminate from the equation (woofy bass, depressed mids, hyperactive high freqs) and then I will start looking at pups that I think will work. Sometimes I'll bounce the idea off of Tim to confirm, but most times I just use this method and I've never had bum choice come my way yet!
As for pushing your amp, a pickup (yes, even the infamous ceramic Warpig) will only push an amp so much and in its own fashion. A great sounding guitar/pickup/amp combination is the best way to go, and then boost as necessary with whatever flavour of boost you prefer (OD, treble booster, fuzz, whatever)
Hope you find this helpful.