go for 1600mhz ram, and 2x4gb instead for dual channel mode. only 1 1333mhz chip running in single channel mode will slow you down.
Not a fan of MSI motherboards. If you're going to go with a 280x, get a good board like
pcpartpicker.com/part/asus-motherboard-m5a97r20
Get an aftermarket cooling as well, like a hyper evo 212 for $30. Even if you don't overclock, your cpu is going to be working and the cooler, the better.