18 AWG is way way way to small of a gauge wire to use for this, at a MINIMUM you need to be running 10 AWG, prob more like 8 ga ( get an amp install kit )
you do have a fuse with in 1 ft of the battery right? if not you can potentialy set your car on fire(esp running 18 ga)
http://www.powerstream.com/Wire_Size.htm
2.3 amps max, your hard drive prob sucks more then that.
other then that it looks good.