In my experience the power level on AMC6 varies all over the place.  Also, not all transponders seem to focus at exactly the same place on my dish.  But take this with a grain of salt, because I'm only using an 18" dish that I didn't have any other use for.  I swing it from 72W to 83W when I hear of a feed I want to watch because I don't have to change elevation or skew.  Sometimes I get usable signal, sometimes I don't.  I've never tried it on my 30" dish because I spent a lot of time getting a multi-LNB setup peaked on it further west and don't want to screw it up.