I have a amp and sub. Stock head unit so im using a line out converter. However for some reason some of the bass still plays through my stock speakers. So theres bass coming from the stock speakers and the subwoofer. So when i turn the bass all the way up through the settings on my stock radio the rest of the music (like lyrics) gets all muffled and stuff and sounds bad. I heard aftermarket head units have something called direct sub output or something where the bass onlt goes to the sub rather than the stock speaker also. Do all aftermarket head units have this? Will adding a new HU make my music louder?