"Move checked to top" works for output devices only. Its not needed for input devices because Sonar recognizes all inputs regardless of the order. There is a technique to it though. For example, if you have 3 outputs and you want to stack them in order, you would do this:
Original order:
3
2
1
Select 1 and click move to top.
Result:
1
3
2
Hold CTRL and select 1 and 2 and click move to top.
If you don't select 1 again, then 2 will be put at the top.
Result:
1
2
3
This hasn't changed since the original version of Cakewalk (pre-Sonar) so I've had a lot of practice with it. They should probably make it drag and drop.