You're probably going to hate me for saying this, but you should get an aftermarket head unit. The SQ will be far superior and it will likely have many more options. I can't confirm, but I highly doubt the factory HU has preouts. If it does, I doubt there will be more than 1 set, which isn't too great.

I grudgingly changed my stock head unit to an Alpine 7894 and I couldn't believe the difference. The SQ is amazing. Time correction has got to be the best thing that's happened to car audio.