Adding amplifier to factory radio

[shanewood911]

Okay I am trying to add a aftermarket amp to my stock radio on my 05 rx330(non mark lev.) But does have nav and iPod hook up. I have a line out converter box (pac sn-35) for adding rca plug ins. Pretty much I need to know how to hook up just the LOC box if anyone knows. Only instructions I can find say hook the 2 gray(right+ right-) to the right speaker output on the car & vise versa for left. But my questions lie in the fact I have speaker wires for (R front-&+ R rear-&+ L front/rear-&+). So im confused what exactly I run the add on wires too. I feel like I am missing an additional 4 speaker wires possibly for the LOC. But truthfully I keep my radio on only the front speakers anyway.