I would recommend an ssd to install your OS. Boot times for all programs and load times for BF3 will be much quicker. http://www.newegg.com/Product/Product.aspx?Item=N82E16820148441
This should be plenty, and you can always place music, movies, and any other files in your Western Digital.
Are you planning on over clocking your processor, I would also recommend a aftermarket cooler for it.