Upgraded from the RS400 to the RSX400 a couple days ago. I was happy with the performance of the original, but the RSX400 is incredible. At full volume and extra highway speed the mesic is loud and clear with no distortion or crackling , just a clean sound(I don't have to run it a full volume, just checked it there) . I really appreciate the folks at Hawg Wired answering all my questions and making it a simple upgrade. If you have a Rushmore Harley these are the speakers and amps to improve on the awesome machine.