Could you please try mudbox / maya maximum polygon count in viewport?
in maya test both Default Veiewport and Viewport 2.0?
While your waiting, there are some YouTube Videos of Maya using a single FirePro W7000, I don't know if dual D500's would equal a single W7000 though.
http://www.youtube.com/results?search_query=Maya+++FirePro+W7000&sm=3