U46mk2 problems in OSX

There's a few problems I've discovered when using the U46mk2 under OSX, which are not show stopping, but very annoying nevertheless. If anyone else has found a way around these I'd be happy to know.
1. Changing the volume of the U46mk2 in sound preferences changes only outputs 1/2. 3/4 AND 5/6 both remain acting as if they were full volume (unless completely muted)
2. Why can't 48000hz be chosen as a sample rate for the U46mk2 under OSX? This is easily configurable under Windows, why not OSX? I believe that outputs 5/6 will not function under 48khz, because of the USB speed at v1.1. This is also not selectable - the card cannot be used in a mode where not all inputs and outputs are active.
1. Changing the volume of the U46mk2 in sound preferences changes only outputs 1/2. 3/4 AND 5/6 both remain acting as if they were full volume (unless completely muted)
2. Why can't 48000hz be chosen as a sample rate for the U46mk2 under OSX? This is easily configurable under Windows, why not OSX? I believe that outputs 5/6 will not function under 48khz, because of the USB speed at v1.1. This is also not selectable - the card cannot be used in a mode where not all inputs and outputs are active.