I am interested in putting in an aftermarket amp and subs in my 3, but I have some questions. Can I make a 'Y' in the rear speaker wire to power a line convertor and still use the wires to power the rear speakers w/o screwing the rear speaker sound up? Also to get both channels working for the sub with only one amp, can I use two line convertors and use a 'Y' patch connecter on each side (two females into one male) to make only one RCA out? Your input is invaluable. Thanks