Well, the first thing I noticed was that you never mentioned whether or not the stock brakes work satisfactorily. Often, "no name" brakes can be miraculously transformed by a simple change of pads. You might try that before springing (no pun intended) for new stoppers.

Second thing I noticed was your comment that the calipers are rusting. I gotta believe that they are aluminum and hence, wouldn't be rusting. With the finishing that comes on most aluminum parts and if you are drying off your bike after riding in rain, etc., I am not sure how they would be corroding so much. The spring I can kind of see, but who cares so long as it's springy (note the high level technical term I used there!).

If you ride in such miserable conditions, get a good set of sealed cables for yourself.

Finally, if you're set on replacing the brakes, the 105's will work with your levers.