There is no need to overdrive the front end with a booster or other pedal. I can easily overdrive the power stage in my 5F1 configured C600 using just the pickups in my guitar. Power amp distortion is a completely different type of distortion and sounds totally different from preamp distortion. Subsequent stages do not "smooth" the signal whatever that means. If they are operated within their design parameters they will simply amplify the signal more. If they are not, they will also distort the signal.