Audio Systems: Electronics in Classic car, classic car owners, rca splitter

Question
I am getting a classic car. Like other classic car owners do not wish to remove the original radio but wnat tunes. The car is a convertible so I am not looking for concert studio sound quality. I have heard bad things about "secret stereo" and products like it. I have a Fosgate amp from my previous car installation. I want to bypass having a head unit altogether and just plug in a portable mp3 player so all that is visible a harness that I tuck away. The rest of the equipment could reside in the trunk.
My question is what should I do about the remote turn on for the amp and will the headphone out to an RCA splitter damage my amp.
Any Suggestions?  

Answer
Max,

 i'm not familer with what you are wanting to do using a portable MP3 player as your head unit, that your completly on your own i dont want to tell you sure go ahead then you fry 400 dollars worth of amps and speakers.. if i've never done it i dont recommend it.. now what i can tell you about is the amp wiring if your MP3 player has 2 preouts *RCA* then you can try it ( i wouldnt ) but you can give it a shot it .. if the MP3 player has only 1 preout and for headphones that is really "iffy" and again ( i wouldnt ) i would say running a headphone jack/RCA cable would get you sound but VERY LOW quality  highs / lows would be distorted..if the portable has double preouts that is your better chance ... i know i havent really helped you out just touched on some things.. if you want some first hand information call both the MP3 maker and the AMP/SUB manufactor ... now for the RMS/turn on .. use your 12volt igntion wire from your fuse block but make sure you run it through seperate inline fuses beside the fuse block .. hope this helps you out sorry i couldnt do more

thanks