It is highly unlikley that you will get near 400w. The rig in my siggy plus a pair of sata hdd's, sata dvdrw, 5x 120mm fans and a multifunction controller only pulls 274w at the wall while running Orthos and Fur stability test at the same time.
I certainly would'nt use a Hiper though. Buy cheap and you get cheap and nasty quality. Look to pay £35+ for a decent small psu. Depending on the rest of your spec you could probably get away with one of the excellent Enemax Pro82+ 385w psu's. I have one powering a ATI 3850 and a E5200 clocked at 3.6Ghz. It only cost me £35 too. Do not skimp on a psu. It is the single most important component in the pc. If you buy a cheap one and it fails then it is more likely to take out other components with it. Hiper's are very good at this!!