Hi, got a question, not sure if I got a bad amp or Im just setting it wrong. The amp is a kicker zx650.4 which is used to power my 4 interior speakers. I am using the hi-level inputs or as they call it speaker level inputs. Now my question is, do I have to set the gain. Cause the gain is set all the way down and the speakers play loud and increases nicely with the deck. But as i increase the gain a little bit up I hear distortion and the speaker goes into protection. I think because the front speakers can't handle the power. But honestly I heard the speaker play louder with my other amp. So is the gain only used with the rca inputs.