There is no pre amp output from our stock system, unfortunatly.
I upgraded my system with speakers, 6 Channel amp and a small subwoofer, but kept the stock deck and changer.
I ran couple of those line converters to get the fading, but you could get one to save cost. Be sure to pick the best quality ones on the market since it will be vitally to overall sound quality.
I have KEF 6.5" speakers F&R, Polk 4 pcs of 6X9 sub (very old) and a Soundstream Continium amp.
I can't say the sound is super good, since I am used to my NHTs at home. It could be best described as Bose AM series compare to NHTs. Not good for vocal music, but great for pop/rock music.