Hi,newbie here.Just bought a 07 S4 and want to add an amp. and sub to the stock Bose system.Search hasn't really helped.CanI just tap into the stock subs input wires-the new amp will have speaker level inputs.Should I leave the Bose sub working? Whats the easiest way to power on and off the amp.Can I tie in to the Bose amp located in the rear,or do I have to go to the HU.(What color wires would I be looking for?)I'V done a couple installs before butI know little about the Bose.( I paid an extragrand for Bose and it %^^&$##%%^&!) Am I missing anything? Thanks in advance.