[JFP in PA]

Depends upon how you define "best"; a used PST II (which is already out of date) will set you back a couple grand. A real PIWIS cannot be purchased, only leased (yes, I know you see them for sale all the time on the web, but they are definitely not the real item), and the current lease rate opens at just under $20K for the first year. The Durametric system is about 75-85% or so as capable as the PIWIS, and cost less than $300 with unlimited updates.