I have a 2009 convertible and because there's no package tray there's also no subwoofer. I'm looking to add one and from everything I have found, it looks like the stock amp has outputs for the sub. The question is, does the sedan have a separate amplifier for the sub and the output from the main amp is just to feed the sub amp or is it actually a usable output? If it's a usable output, does anybody know the wire colors for the amp and what the impedance of the stock sub would be?

Thanks.