I just bought a sub and amp (should arrive soon) for my Mazda 6 and I'm super pumped and then my friend asked "you're sure there's a port for a sub in the unit right?".... Um no I'm not sure. And if there isn't do I need a totally new stereo? I kinda just blew all my money on the amp and sub (I'm in high school). So if anyone knows how I can hook up a sub to this please let me know, thanks!