power question, i need power for my cooling fans Options

[whitefuzz]

FINALLY i have a holiday! (3 weeks)
so now i have the time to take care of the setup of my trunk i've been planning for a while now

still have a question:

my amps come under plexiglass
that will look sweet but that way they're also in a little box witch will get filled with hot air once the music starts
that air should get out so i got some nice pc casemod cooling fans

now i m wiring these

they should start spinning when the radio starts to play but i can't put em on my remote cable
so i m now looking for a cable in the car that has power when i start the car
en goes back to nothing when i shut down the car...
that way the fans will start spinning when i start the car & stop when i shut it down...
that should give the amps a nicely cooled "box"

now my question : where can i find that wire?
doesnt really matter to me wich one
but it should have power when the car starts en return to nothing on shut down...

i thought about the cig lighter cable (cuz i'm removing the cig lighter and replacing it with my remote bass control button) would this be a good idea?