I curretly have a Clarion db455mp installed in my 97 infiniti i30. I like the way it sounds but it lacks a sub adjustment. I'd really like one, and I found out for the price of an amp adjust knob, I can upgrade to the clarion DXZ655MP. I know it had 6 rca outs instead of 2 and they are powered (2v i think). Is it worth it to upgrade decks or should I just get the knob?