What are your current speeds (both down and up)?
I don't think VanBuren has a .css file for your exact amount of speed, so I'd use both the higher and lower (for example 6-8/1 and 5/768) and see which one gives a faster and more stable speed.
You may also get lucky and get a custom file just for you.
Note: You may want to put another 256 ram stick in your system, it's cheap and the benefits are sometimes quite big, especially going from 256 to 512 or higher.