Anyone convert to a Mach 460 soundsystem?

My girlfriend has an 03 with the standard sound system but does have the CD single disc player. Are the harnesses completely different from the head unit back to the rear speakers on cars with the mach 460 system. I know that the standard systems did not have amplifiers in the rear but not sure on the front. Just curious what harnesses are needed in the conversion. It'd be nice if the harness was prewired for the amps so i wouldn't have to tear the interior out of the car to run the new mach harness. Also, does the 6CD head unit use the same harness as the single cd head unit? I know that a CD harness is needed when going from standard AM/FM to CD, but i already have a CD player. Just wanting to upgrade to the 6 CD. Tips, advice, or experience on doing this is greatly appreciated!!!! Thanks

Thanks for the info. Newer cars have special harnesses for their CD players and speakers. I know you can buy the connectors to adapt an aftermarket head unit to the factory harness, but what do you do about the speaker connections? Mainly i was just wanting to add the 6 CD head unit, the speakers at the top corner of the doors and the 6x9 speakers in the rear shelf with the amps. I guess the amps are what causes all the headaches.

Any idea if you can add the tweeters to the doors on a standard stereo system? I just got them for $40. If anything i can splice the wires going to the door speaker and have them run on the same circuit.