I'll be putting a factory sub into a vehicle that didn't come with it in the next few days so I can check the wiring.

Personally I will be using an aftermarket amp for the subwoofer so I won't have any info on that but I believe that you need a DSP amp to be able to use it.

The previous X I had did come with the DSP option and I'm pretty sure I removed that amp before I scrapped the car so I'll try and have a look to compare both amplifiers.