Came on here a few months ago and got got some great help from a few posters who told me how to add an aftermarket amp and sub to my lackluster Bose system in the 07 Tahoe. I was instructed to tap into the sub line under the center console and run the hi/lo from there to the amp. I went to a local shop, highly reputable and recommended from an audiophile friend, and gave them SPECIFIC instructions to tap into the sub line, and ONLY the sub line. What happened? You got it, they went into the side door speaker wires and it worked off and on for the next few days. Every time I got back into my truck I had to pop open the fuse panel and reset the converter until they could take me back in the shop. I asked them to rewire...what did they do? Replace the hi/lo in the same location. Total tards. After going back again and demanding my install fee refunded (they had even written my initial intructions in the work order so I was successful) they rewired into the subline and it has worked flawlessly since.
Bottom line, if you plan to attempt it yourself be sure you get the right wires. And if you take it to a shop, even a good one, make sure they truly understand before you walk out! Good luck!

 

Its like most things in life. If you want it done right the first time, you almost always have to do it yourself. Every once in a while you find somebody who will fix your stuff like its their own. Those I am willing to pay a premium to.