How Do I set up my subs to my stock head unit?

From what I can tell, it looks like the second one will accept a signal from your regular speaker wires, but you will probably have to disconnect the rear speakers in your car. At least you won't have to fiddle with the head unit at all.. But I always say if you are going to do something, do it right. Wait till you can get a new head unit with pre amps. It will probably have a better built in amp to power the rest of your stock speakers as well. Definitely worth it.