AG, in my experience the amount of SA introduced by the viewer itself is very much dependent on the focal ratio of the light cone from the scope. In the case of the Cass's and refractors you have listed, your "fastest" scope is F8 and that should not be an issue. Only when you get to F7 and faster, could it be an issue. Now if you want to use a Baader or other prism diagonal as well, that's different and I would recommend a GPC for use with any scope faster than F9 or F10.
You have to use GPC's and spacers with the viewer to reach focus with your Dob.