I recently had a Kenwood DDX-419 professionally installed by a local car audio shop in my 2007 Xterra. They also ripped out the stock speakers and replaced them with Memphis speakers.
The bass and mid audio seem to be playing great. It's the highs that are just too high, and seem to distort at a volume greater than 20, which really isn't that loud yet. I'd like to dampen the high frequencies a little and take the edge off if I could, but no matter what I do in the EQ, it doesn't seem to help.