You've posted this question in another thread already. (See here
My answer's posted there, and judging from your statement: "A tripod will be used with the ND filter so I am thinkin get it a little dark in which I could bring the F-stop down to bring in more light, rather then only to find out still too much light with the ND filter in use." - you don't quite understand how the ND is meant to work.
You just run a longer shutter speed rather than alter the aperture, which will in turn affect your DoF. The longer shutter speed allows moving things to be blurred.
There's also a search function for the forum - you'll find lots of information about using ND filters already posted.