2000 eddie bauer explorer sub bypass

hi , i have a 00' eddie bauer explorer with the factory amplified system. what i want to do is ,upgrade the factory amp and sub with a mtx thunderform sub box and amp. the problem is ,that i want to keep the factory headunit with steering wheel controls and the disc changer. do any of you have any ideas how to do this? is there special harness adapters that in need? thanks for the help !

Here is a harness: http://www.crutchfield.com/S-A6j6jVBLmK2/cgi-bin/prodview.asp?i=120705517&s=0&cc=01

i not 100% sure, but that looks like it is a receiver harness to put a aftermarket radio in and retain the factory sub. i want to keep the factory radio and changer, i just want to put a new sub and amp in.