Need Help: Mach 460, replace HU w/aftermarket, w/o bypassing amps, and add sub

[JordanB21]

1. Basiclly I want to install a new headunit while still using the entire mach 460, including the two amps in the back and speakers. But also I want to be able to install another amp and subwoofer in my trunk. To me this sounds like a pretty decent idea, I would be able to keep my highs on my tweeters, my mids from the back amps, and then have lows that are controlled through the aftermarket HU.
2. Here's the complications though. I've never worked with sound systems before, ever(I'm 17). There was once an aftermarket headunit in my car that was stolen out years ago so the wires were then plugged back into a stock headunit. This means that the wires are all cut behind the headunit. There was also a bypass originally done, I undid this and returned the amps back to working so I doubt this'll effect anything(just a note). At a point though RCA cables leading from headunit to trunk were laid, along with a power wire to the battery, and a blue(I guess system control wire?), to the head that aren't in use. Sooooo, I figure this can be used for the aftermarket amp and sub.
3. To the questions(!): Is it possible to keep intact the stock 460 amps with an aftermarket HU? If yeah, how can I do this? How many preamps would I need in my headunit? Well, I guess I didn't have many questions. That was about it, I believe. Oh and this is in a 1995 GT.

 

[Routs]

In the most simple sense, yes this is easily achievable. All you need is an aftermarket deck that has RCA outs and an adapter to connect your deck to the factory wiring. Then your deck will play through the factory amp and speakers. Then you'd run RCAs from the deck to where you wish to install your new amplifier.

As far as ease of completion, its really not that bad. We've all had to start somewhere. The most difficult task you'll face is connecting the wiring harness from whichever deck you purchase to the adapter harness you get. The easier way is crimping the matching color wires from both harnesses with pink dog bone connectors. This way takes less skill but some hate this way as connections can become loose or corroded if not done right. The best way this is done is by doing one colour at a time and then using good electrical tape to seal area around each dogbone connector.

The better way is to solder each connection together and cover with heat shrink. Either way it's reasonably easy if you take your time. The better you do the longer your install will last.

 

[JordanB21]

Alright sounds pretty straight forward, I'm sure i'll go the easy route with attaching the wires though(Easier to undo for trouble-shooting). Mostly about getting the money together in the next few weeks or so
Would this adapter be what I need?
http://www.crutchfield.com/p_120705510/Receiver-Wiring-Harness.html?tp=2977#overview-tab

 

[Routs]

That adapter will work if you wish to use your pre-outs to go from the new deck to the stock amplifiers. If you wish to save your pre-outs for your own aftermarket amps, use this one:

http://www.crutchfield.com/p_120705002/Receiver-Wire-Harness.html?tp=2977

Either way works, it just works in a different fashion. By using the pre-out method, you'll be allowing the stock amps to only receive a basic signal and not over amplify a signal already amplified by your deck. If you still wish to add your own amplifier though, you'll need at least three pairs of pre-outs coming from your deck.

 

[JordanB21]

Okay, looks like im set, thanks for the link and the better way to do my set up. Now just have to group the money and go shopping.