You probably don't want the 500W builder series supply. Go with an XFX 550W or something with a little more headroom. The required wattage ramps up quickly when overclocking.
WD Caviar Blue is great for budget systems, but will not make for a very good desktop experience. At a minimum get the Caviar Black, or a Seagate Barracuda. If you can increase the budget, work a small SSD in there for the OS.