What is your budget? Are we working with some sort of limit?
I'd switch out the WD Blacks for Samsung F3s. They're faster, cheaper, and more reliable. You better get them quick before they disappear since Samsung sold their HDD division to Seagate.
The RAM is ok, but depending on what you're paying for them you most likely could get better. I'd personally get a DDR3-1600 kit that has a lower latency (8, or even better 7).
You could EASILY spend less on a motherboard. The Sabertooth is built more for gamers and is very expensive. I'd recommend getting a less expensive board because you don't need things like SLI/Crossfire capabilities and such.
Good case, but check to make sure the 6950 will fit properly.I'd also recommend the Cooler Master HAF 912/922.
WD is managing to sell the 6Gbps Blacks simply because the average consumer thinks it makes a difference. The problem is that the platters can't physical read or write data quickly enough to take advantage of the bandwidth increase.