Here is a step by step for installing a powered subwoofer in the X:

Remove ashtray. Turn key to on and then move shifter down to D. Turn key off.

Disconnect negative  battery cable.

Pop off gearshift surround (wood). It just pries up with your fingers. Start at the front edge.

You will now see two phillips screws at the bottom of the console. Remove the screws.

Pull out the ashtray area - disconnect the 12v cig lighter socket and put assembly aside.

With something soft or a careful scewdriver, gently pry between the hazard flasher button and the seat heater switch (or blank if no heated seats) - then remove the upper wedge area of the console.

You will now see 2 torx screws. Remove.

The entire unit can now be pulled out. NOTE: PLACE A FEW CLEAN RAGS OR TOWELS DOWN OVER THE SHIFTER AREA AND CONSOLE TO AVOID SCRATCHES/TEARS. The edges of the unit are very sharp - so protect your area.

You will now see the wires in the back. The main stereo unit wiring is on the left side (looking at the unit from the front). You need to pull the wiring harness out of the unit. Press down on the top of the connector and wiggle it back and forth to remove it from the head unit.

You are now ready to do your splicing. This will vary depending on what exactly you are doing.

My Kenwood unit has a power, ground, remote, and 2 speaker input leads. I ran the speaker leads under the rear seat, along the door sills, up over the drivers side footpedals, and into the back of the console. You also need to remove the drivers side console cover (carpeted) if you are going to wire the same way. To remove that, it has one phillips screw by the drivers seat. Then just pull it back and it pops right out.

Okay, the speaker wiring: Right rear speakers are: left rear are white/green and yellow/red. The left rears are white/blue and yellow/blue. To splice in, I used a utility knife to carefully remove some of the wire covering, then I soldered in the speaker input leads to the amplifier. (I'll have to double check + and - colors - I'll update later).

The power lead is brown with white stripe. You can splice your power lead for the amp here if you don't have power in the trunk. I had a cd changer in the trunk already, so I just spliced power, ground and remote from there.

Remote turn on wire is yellow/green. Ground is black - however I would ground the amp next to it's mounting location on bare metal to avoid ground loop noise.

I used zip ties to secure all of the wires. It is VERY important that you secure the wires that go over the footpedals to mitigate the risk of them falling and getting caught on your foot.

The unit that I installed was a Kenwood 10" subwoofer box with built in 200watt amplifier. It also comes with a wired remote control to make adjustments to the bass. I ran the wired remote under the door sils and secured it with velcro tape to the carpet side of the console kick panel on the drivers side. The unit was on sale at Best Buy for $139.00. It sounds great!

I also spliced in an additional 12v cigarette lighter type outlet for my Sirius. To do this, I simply spliced in to the power leads to the factory cig lighter outlet and mounted the new outlet inside the center console.

I have a picture of the head unit out of the car with the wire connections, I'll get it up hopefully this evening.

Total install time was about 2 hours. Tools needed: utility knife, phillips screwdriver, torx bit (I'll post the exact size soon), electrical tape, soldering gun and solder or some type of wire splicer or nuts, wire stripper pliars are nice but not absolutely required. That's about it. Just take your time!

Please feel free to post questions!!