2011 Lexus GS350 non mml how to add a signal processor
 

I'm looking to add a the audio control lc7i then adding a 4 channel to the interior speakers to add a Lil more highs and mids and a mono amp to a Jl sub. My question is where do I connect I know the amp is in the trunk but do tap directly to speaker lines off the amp is it pre or post speaker wires that I connect to? Any help would be appreciated thanks