Dumb questions re: aux-ins and amplifiers

Greetings all,

I have been trying to piece together everything I need to know to get this done right, but the info I find is either incomplete or conflicting. Here's the deal: after installing a carpc in my 300c and having fair success, I decided to put one in my HOV car, a 2004 Prius. I am getting some hum, although unlike with the 300c it doesn't change pitch when the engine RPMs change, though it does get louder when I brake (which may be unique to the Prius) however. Here are some key points and questions:

1) I am using an amplifier in both cases, mainly because neither car came with an aux in. Now that they are available, if I get something like a PAC AUX-BOX that connects to the CD changer port on the back of the factory radio, and I plug in my car PC to the aux in, will I get sound out of all my speakers or just the fronts? If all, I presume it is the car stereo cloning the signal to the rears?

2) If I stay with the amplifier, and I mount it somewhere mid-vehicle (such as under the passenger seat), is grounding to the rear of the vehicle (about 7 ft of cable) with an 8 or 10 gauge wire sufficient for a 350W amp or does it have to be much shorter? If it must be shorter, how do most shops ground amps that aren't in the very back or very front near main ground points?

This should get me started - thanks!

 

<div class='quotetop'>QUOTE(Presto @ Dec 12 2006, 01:27 PM) [snapback]361135[/snapback]</div>

I can't remember the model at the moment. It is a Phoenix Gold digital amp w/optical and RCA ins and 5.1 capability. It is only 4-ohm stable (plus 2-ohm for subwoofer) so it is small. I was looking at putting it under the passenger seat...

 

<div class='quotetop'>QUOTE(eagle33199 @ Dec 13 2006, 06:41 AM) [snapback]361431[/snapback]</div>

Yeah, nothing there. I have the basic non-JBL system. Thanks for the info - I think that is where I am going to try it.