not sure how many additional devices you will be adding, ie. PCI cards, USB devices, etc. Generally all you need is ram, video, cpu / hsf, power (duh), HDs, optical drives. personally i would boot and install / update my OS to the latest & greatest as well as update all of my device drivers. then you can add USB devices one at a time, if need be.
one of the old rules of thumb is to leave the case panel off if it's your initial build - it's considered bad luck among builders to close the case before attempting to POST! 😉 at any rate, good luck with your build - let us know how you make out.