I don't use a canister so will let others talk with you about that. I do know that the Marineland 400 is a good filter, though. If it is too noisy, raise the water level so that the water returning to the tank doesn't have to fall far. That will reduce the noise level drastically. How often do you change the cartridge in it? If you feel that the filter is not doing its job, maybe the cartridges are too dirty. Also, how often do you do water changes and vacuum the gravel? Doing that at least once a week will reduce the smell.
Your Silver Dollars should be in a group of at least 6 individuals because they are a schooling fish. They also eat plants so watch for that. Here is their profile: http://www.badmanstropicalfish.com/profiles/profile23.html