I recently built a spec ADA stand for a 90-H. 3/4" plyboard is plenty strong for your application. If I were ever going to build another ADA stand I would be tempted to use MDF. Finding plywood (even furniture grade) that isn't warped to some degree is damn hard. And even if it isn't warped at the time of purchase that doesn't guarantee that it won't get that way. Getting straight cuts with slightly warped plywood is a PITA! Bottom line, decent cabinet or furniture grade plywood is more than enough for the size stand that you are proposing to build.