I have an 01 Mazda Tribute.. I want to keep the factory 6 disk changer, but add my sub amp, and possibly my 4 channel amp. To keep it simple on me for now, though, I just wanna get some bass. I bought a line output converter because I know that's how it's done, but as I was reading the instructions, I got lost. There are 4 options. High to low converter, High to low (sub amp only), Common ground system (for old cars.), and the common ground for bose and jbl radios. I have a "premium sound" system in there, but can't remember what brand. I am good with stereo typically, but have never dealt with a factory h/u. The more help you can give (detailed), the better.. Thanks in advance..