Whoa this thread has really gone to town since I have been on the back burner!
Your canister is going to be drawing water through itself and back out underwater, and just like a swimming pool the water gets
O2 right from the surface - no problem. The water is constantly moving and that is where you get your
O2. If for some reason you need to increase aeration while (*crosses self*) you raise the temp to treat for ich, or whatever, you can just slide the spray bar up on its little suction cups and get your splashy action.
You are going to be so happy with the quiet unobtrusiveness of a canister, but don't forget these can be a nitrate factory so if you begin to have algae problems or an unexplained nitrate spike that you can't seem to control, increase your canister maintenance.
I don't recall in this lengthy thread whether cryptocoryne has been mentioned, but you certainly need nothing fancy at all for that, and it will, over time, spread and create very nice stands of plantings for you. As long as your substrate is not too large and is small gravel you could plant that. Marimo balls are also nifty low-light plants.