Bose sound system, sub install

[NVE THIS]

I've got a 2003 Yukon with the Bose sound system. Does this mean I have the LUX model in the event I wanted to buy a GM Navi radio from ebay I should look for the LUX one?

 

Also, I don't have the rear Sub. I'm trying to install 2 12" subs in the back keeping everything stock. I bought a 2-ch line output converter for my amp and spliced the rear L/R channels behind the radio. From speaking with ore of my friends, there is not a lot of voltage for the LOC, but if I tap into the L/R at the Bose amp it will sound better. Anyone know where I can tap the L/R channel at the amp and what wires? thanks.

 

Bryan