First off, tell him to drop the Behringer. There are WAY better amps for the same money. A vintage music man 2x10 or Roland jazz chorus can be had in the $350-$500 range.
I can't tell by your description what sound you're going for. You've mentioned hardcore, and alt-rock (the latter being a pretty general term). If you want some hardcore crunch out of a strat, I have two suggestions- (1) Big Muff. I don't why this particular distortion pedal works better with single coils, it just does. And, there's less to fiddle with, which sounds like a good thing for this guy; or, (2) if he insists on the Boss, have him buy a hot rail (it's basically a humbucker turned on its side to fit in a single coil slot). Seymour Duncan makes a nice one.
If you want a good alt-rock sound, go with the aforementioned amps; or, if funds provide, buy a really good vintage amp like a Fender Twin reverb, Orange, Vox AC30, etc. There are good tones to be had in Boss distortion pedals, but only after much tweakage and with very particular pedals. He might try an ibanez tube screamer, or even Boss's blues driver.