Alexi uses an emg hz-4 humbucker which is pretty blusey, but after adding loads of distortion, you get that certain tone like he has. I got that humbucker and put it in my Shecter, the leads sounded awsome, but the lows just wern't cut for metal. It all depends on what your setup is.

I too would like to know how some guitarists get that "beep tone." The best example I can give is Back Dahlia Murder's lead tone, it sounds so awsome.

PRSPlaya is out best bet, he's a tone whore. :D