I would opt for a little bigger power supply, not that you absolutely need one....just to give you more room for future upgrades ect. How about a CORSAIR Builder Series CX600? It is 170 watts more for only $10 more, and a much better overall product.
The Corsair has 1 single 12V rails, instead of 2 like the Seasonic has so you won't have to worry about load balancing. Additionally, the Corsair has a combined total of 46amps on the 12V rails, while the Seasonic has 34 Amps.
Also, how about a SAMSUNG Spinpoint F3 HD103SJ . It is a bit faster than the WD blue, and a bit more reliable for $5 less!