That is the easiest way. (low line convertors) Just make sure and keep your ground for your amps away from any other wiring.

 

This thread got me thinking about my truck. I go outside & yup harness (zero slack in it though) under back seat. Pop the dash/radio & I found 2 connectors in dummy plugs. The radio also has what looks like a receptical for a 8 pin connector in the lower middle (like the sub connector in the back), one large harness connected on the drivers side, & the antenna conector on pax side. Here are the 2 unused connectors

1st connector- small flat 4-pin on A/C control harness in a dummy
plug taped to the harness colored as follows=
1) RED/WHITE
2) BROWN/WHITE
3) PURLPE/ORANGE
4) BLACK/BLUE

2nd connector- slighly larger flat 4-pin on radio harness in a
dummy plug on back of coin holder colored as
follows
1) BLACK
2) BLUE
3) BLUE
4) LIGHT BLUE/RED

 

I have an 07 f150 xlt. There are tweeters on the door. Are they powered by the same wires that do the speakers on the lower part of the door or are they seperate. When I wired my harness on my alpine there are just right and left +&-. I didn't see anything on the harness for tweeters. I just thought I would ask since it doesn't seen that the tweeters are working after the aftermarket HU was installed. If they are, I need to get a corss over for them then since i can't tell. Any easy way to test?