I have an 09 silverdao w/the bose system, and i am installing an aftermarket amp and subs to the factory head unit. i am wondering if it makes any difference if the line converter deal is spliced into the rear speakers before or after the factory bose amp. i have called around to a few local audio shops, but have had no luck. i have this installed right now, and it just seems like it hits a little weak. i have a 1000 watt 2 channel amp, and 2 10" kicker solo's. this was out of my friends 98 silverdao and it seemed to hit a little harder....

 

you're gonna want it to be installed after the amp. The line level converter takes a high level input, converts it to a low level input that the aftermarket amp can use.
If you get it before the amp, you will take a low level signal, take it down even lower when sending it to the amp