As I stated earlier, I don't think the volume of the shutter really matters. But since we are discussing the finer points of what is quiet and what is not, I think that there are only two EOS cameras worth talking about: The EOS RT (the model whose name escaped me in my earlier post) and the EOS 1N-RS. Nothing will be anywhere near as quiet as those two.
The RT is older, and based on an amateur body. It is small, light, slow, and fragile in comparison to the 1N-RS. The 1N-RS is a brick of a professional camera that you could probably use as a hockey puck. It is quick and full featured, but large and heavy in comparison to the RT. There are times when I would want the RT and times when I would want the 1N-RS. I would generally prefer the RT for street photography, because it is light and small. But if I wanted close to the best auto focus and speed I could get, I would need the 1N-RS.