I think I found what alot of people have been waiting for. Its not cheap $150
but if you want to use your factory amp setup with aftermarket Deck, here it is.
I don't know who makes it ,just know where you can buy it. I dont see anything
other then this for the 2008 9 speaker setup. I hope the mod. dont delete this link
this might help alot of people.

http://www.autotoys.com/x/product.php?productid=6405

 

Has anybody used this device on the rockford system does it work?

$150 is not bad, but for a little more, I can get into an after market amp.

Would it be possible to simply install an Amp in place of the stock one and get the new amp to power the existing speakers, including the sub?

Keep in mind my target is not to have a loud system as much as it is to install a nice HUD and get decent sound from it hopefully using the factory speakers. I am trying to upgrade the HUD without changing the entire system and this device seems like the key to it all, just want to make sure it works while i am evaluating my options.

 

I checked with autotoys.com and they have no firm date as to when the product will be available - they said it was in final testing stage.

Chatting with installer.com support indicated that it will be "a month or so" before it is possible to turn on the factory amp with an aftermarket head unit.

Now, my question is this: Is it possible to replace the factor amp with an aftermarket amp and run the factory speakers, including sub through the factor wiring?

I understand that the stock speakers /wiring will do no justice to a decent aftermarket head unit / amp, but right now, i just need to know whether its possible - not so much that its a bad idea.