Ok so heres my question, im going to run 2 kappa perfect 12.1s off of a PG r15. I am going to splice into both of my rear shelf speakers and wire them in parallel. should i splice into the wires before or after the factory amp? i am going to use a line output converter either way. - also will the subs peak at about half volume? some circuit city idiot told me that when i turn it up to half the subs will be at their loudest and if i go up any higher, only the interior spekaers would get louder and the sub would get quieter. is this true?