your temps are ok for a stock cooler. The idle may be a little high (depends on the temp of the room its in) but 57 at full load is nothing at all to worry about.
I remember my X4 955 with the stock cooler was seeing Idles of around 35-40C and full load of around 50-54C. (The difference most likely due to ambient differences I'm guessing)
If you're concerned, you can get either TX3 or the Hyper 212+/EVO for a little peace of mind