I've received the harness for the Mach 460 factory connectors.
I tested it with a Mac Laptop and the output volume is "fair". The "Line Out" signal from the Laptop should be amplified a little more to meet the input levels of the factory amplifiers. (Or maybe it's about the impedance from the "Line Out")
I'm trying to find the Specs from the Mach 460 Amps to be sure.
I've used to have a Pioneer stereo connected right from the amplified output to the Mach 460 amps and everything was working fine.