I have a 100 watt Marshall amp among other toys, I tend to get the best tones by keeping everything between the 6 and 8 on the dial including presence and distortion. Going to 10 on the distortion won't give you the best tone, that's my advice.
Also, strat-man is absolutely correct, tone is 99% in the fingers. If you are tweaking for a lead tone you should try sliding into a note and doing some heavy vibrato everytime you tweak the settings - as opposed to just picking an open string like most people do.
For rhythm, if possible, get a friend to play a riff that involves palm muting and open strumming over and over while you tweak the dials to your own liking. When you get a sweet tone write the settings down or take a photograph on your phone - it's all too easy to lose the sweet spot by brushing off dials while moving your amp around.