I have an s4 b5 avant with synphony system non bose. I am constructing a sub enclosure for the pass side where the standard crappy audi sub is, What do i need to do to get the rear speakers back on once the standard sub is removed? am i better getting an amp to run the rear speakers and an amp to run my sub, an amp for both sub and speakers or can the standard amp be taken out of the audi sub box? which is best and what would i need Also I take it i would just need to run it on a line level converter? Not sure what size sub im gonna run yet, just gonna see what volume i can sensibly get without ruining boot space.