First off... I would highly recommend looking into an inexpensive thermal probe or maybe one of the front mounted panels that have probes included. Asus Probe has a well earned reputation for being about the worst possible way to monitor temperatures.
As to your motherboard temperatures, they usually only tell you if you need better case cooling or not. The processor temperatures are the ones that will have the most meaning. Also, this particular temperature can vary a lot between boards depending on where it is located in reference to the major heat producing components (video and processor mostly).