the kit fitment thing I discussed is far more easily understood when you have the H/U and kit in your lap ready to assemble.
Wiring for my car after I get the SVXdc harness in the mail will be as follows. The H/U has a harness, the ASWC has a harness, and then there's the 3rd harness, in my case, from SVXdc. You wire the H/U harness, and a few of the wires from the ASWC harness to the SVXdc harness. Once those are wired, you simply plug the SVXdc harness in to the car then plug what needs to plug in to the H/U and you are good.
Think of it as if the H/U and ASWC and SVXdc harness are triple teaming the car for some dirty audio sex, but the ASWC and the H/U and 3rd harness are already humping eachother while they approach the car's harness. pretty disgusting, eh? but you won't forget how it works.
make it easy on yourself and buy the 20pin forward harness from SVXdc. It's under $20 shipped and he adds the SWC wires for you, so there's no chance of F'ing up your car's wiring by having to tap into or cut them.
here's a pic of the SVXdc harness that I ordered to replace my currently installed one. My only regret is that I didn't buy this first: