I think coarse/fine is all you need. If you plan on doing any heavy stock removal on your knives (like thinning down edges), you might consider purchasing an XXC stone (only available as 8" diasharp), and if you ever use push cuts (most cuts are slice cuts, IMO), then you might consider also getting an Extra fine stone as well as the Extra Extra fine stone (the EEF is only available as an 8" diasharp). The edge the fine stone puts on will hold an edge a long time and you can get your knife very sharp with that finish.