The switches on the Renegade ( or any amp for that matter) are to give you a variety of sound choices. If you find a certain setting does not sound the way you like, just don't use that setting?? The 18 watt setting will sound more compressed and muddy than 65 watts because you are overloading more stages in the amp. I assume this is more apparent at louder volumes? Once you use up the 18 watts (or 65 watts) turning the volume up more will just cause the power stages to squish and compress more.