Hi, I am a new X owner(2002 silver ice SE 4x4). I was pleased with the stock audio system, however I wanted a little more bass but did not want one of those big sub boxes taking up all the room behind the rear seat. So I went to a local audio store and had a Kicker Solo Baric 8" square sub with a factory built box that is approx.14x6x4 installed, it is powered by a Kicker IX402 160 watt amp. I also had a switch built in to turn the signal and power off to the amp so that I can easily disconnect the sub if I need all the room in the back. When I let someone listen to the system, I open the hatch and show them where all that low-end is comming from they can't believe it's from that tiny box! Give one a listen, you won't believe this small set-up can crush your head like a peanut.