We have an '04 Accord V6 coupe with the factory 6-disc CD player. What is the cheapest, easiest way to add an aux-in to the factory unit?

Also does the factory unit have any pre-amp outs to feed an amp, or should I use the rear speakers as a signal?

 

an FM Modulator is the cheapest, easiest unit. hard-wired sound better than wireless, but hard-wired is more expensive.

just use the rear speakers. get a LOC with auto turn-on or an amp with auto turn-on to eliminate the need to derive a turn-on at the dash.