If you plan on having an Amp or other electronics in the future in your car I highly suggest building a seperate circuit with fuse for you setup. Buy some 0/1 gauge wire and run it from the + battery terminal to a distribution block somewhere under the passenger floorboard. Make sure you have a 30amp inline fuse between the battery and distribution block. Then run a 10 gauge wire from the block to a 30 amp relay. Have this relay activate when the ignition is switched (aka tap the ignition switch wire). Now run the ouput for the relay to a distribution block. This is a source for all your ignition switched power sources. Put this stuff in a small box and you have an easy time wiring things up.