I used to have a complicated adapter like that with my Mach 460, but I found a cheap one from Metra that's designed for the Mach 460. It's model number 70-5514. I use that exact one with a Pioneer in my Mach 460 without problems.
Of course, this sends the amplified audio from the head unit to the amps, so I wouldn't crank the volume too high. The fancy adapter from Crutchfield will simply help keep you from shooting yourself in the foot and cranking the volume too high.
Careful you get the 70-5514, not the 70-5519. The 70-5519 is for the 99-04's, and won't work with the 94-98. I made that mistake.
I might give that harness a try. As far as the amplified signal going to each speaker, maybe I could add the gain box from the scosche harness to the metra harness? I may try that. I listen to my music LOUD so I'm a tad worried about blowing the speakers.
