Lots of good info here, albeit some of it is over my head!  I was hoping someone could give me some actual hard costs on what equipment costs.  I can handle the networking side of things here at home but based on what I'm hearing I'll never get that far.  Fortunately my current solution works perfectly so I don't need to change.  I have two providers I can use that cover my entire area and give me sub-inch accuracy.  I think I'll stick with them.