If its for recording purposes, just be careful as more often than not extra gain just ends up sounding extra mushy. Your guitars will lose note definition and clarity with too much gain.
A heavy live guitar sound rarely equates to a heavy recording sound. IME its the bass guitar and kick & snare drums that bring the heaviness to a track. Might sound a bit "wimpy" on their own, but often less gain gives a better overall mix.
Anyways, as for pedals, Ibanes TubeScreamer is great for pushing tube amps. Digitechs Bad Monkey
pedal is great also. Dont let its low price fool you, it is a very diverse and great sounding pedal.
Anyways best of luck...