I have had the R3A and still have my R4A. They are entirely adequate in terms of build quality for all normal photographic purposes. I would not recommend them as a substitute for a hockey puck though.
You can get all the information you want on all models by first going to <http://www.cameraquest.com/canonp.htm> to review your existing camera and then hit the "home" button to get to Cameraquest's very comprehensive Voigtlander pages.