Can I use the stock amp for just the back speakers?

[ThePhobos]

I have a GT-S with the 8-speaker system. What I want to do is to replace my front and rear speakers with aftermarket speakers, replace the head unit, and add subs. Although my Alpine head unit has a built-in amplifier, I'm guessing that the amp that comes with my premium sound system might put out more watts. I will be running my subs and my front components off of two separate amps, but I wanted to run the rear speakers off of either the stock amp or my HU. So here's a slew of questions I have....

1. Any idea how many watts the stock amp puts out per channel? My radio can do 60w x 4, though I'm sure that's max, so it's probably 27 RMS or so.

2. If the stock amp has more watts RMS, how can I wire it so that I only use the amp for the rear speakers, but bypass the amp for everything else?

3. Do I need the Scosche TA03 adapter to be able to do that?

Not as many questions as I had thought, hehe. I'd appreciate any help I can get. Thanks!

[GTSDOHCVVTLi]

1. The Alpine only puts approx 17 watts RMS. What model is it?

2. To do that you need the Scosche adapter. If your Alpine has 3 sets of preouts, you can leave the front channels, used the RCA on the adapter with the rear output preout on you HU, and run the the front spkear channel to the output side of the amp and tie it in with the right spkr leads. Connectt he Sub preout to you subwoofer's amp

3. Yes

[ThePhobos]

1. The Alpine HU I have is the CDA-9815. If you hook up the power wire to a source other than through the usual harness of a factory radio plug, you get enough power for the radio to use it's built-in amp that is 60w x 4. So you're saying that should only get me 17w RMS?

2. If I'm reading you right on this, basically just plug the rear RCA plugs into the amp and bypass everything else? My HU does have three preouts.

[GTSDOHCVVTLi]

The headunit is actually rated at 27 watts RMS. I have no idea what the OEM amp is rated and cant find that info anywhere. I know though it sounds pretty damn good with my CDA-9855.

2. yep. and wire the 12v constant power accessory power, gorunds, and illumination. run wire for your front speaker out to the output part of the OEM amp harness

[ThePhobos]

Awesome. Thanks for the help. :)

[GTSDOHCVVTLi]

NP if you need the wires ID's let me know and I'll mess with the OEM amp and find the wires