Distortion pedals as boosters? Thats like adding an extra gain stage... a pure booster is something that boosts volume. Throwing a distortion pedal before a distorted amp only adds more gain, not so much on volume.
So as an gain booster... its usually used before amp so its guitar to booster to amp.
Usually, the pedal is set with little distortion, but lots of level. Then tweak your amp's gain appropriately...
The mistake most newbies make is that they throw max distortion on pedal, and max gain on amp... get lots of noise, then say that the pedal and amp are horrible things.
Its always, minimal pedal gain and max pedal volume/level. Then don't set the amp's gain too high,... tweak around to find an acceptable gain level with minimal noise.
So you would prob have something like a crunch to chugga chugga mode with the distortion pedal as a booster. Or a rhythm to a lead mode... although, unless you are the only guitarist, you wouldn't be able to cut thru much without some help from a vol boost or major tone altering...
Hope that helps.
