Seems a little high - which Asus MB - usually you can find this type of information on the internet if you punch you MB model and "operating termperature" into Google. I run an MSI K8N Neo 4 Platinum and the "system temp" is typically 30-34 deg C but can get up to 38 if the room gets hot. Usually my CPU runs at 38-47 deg C again depending on the room temp and the program I have just been running. Prime95 is good for putting everything under load to get an idea of the upper limits
X38 is a very full-featured high-end chipset, so it will tend to run hot, whihc is probably what is causing the high motherboard temperatures. My P5B-Plus(P965 chipset) is at 36c idle right now, so your temps aren't anything to be worried about.
Do you have good case ventalation GOOD I mean flow. I have one 120mm that works better in my setup then the 8 80mm fans I had and I cant even hear that fan run its turned down so low. CFMs dont mean better cooling. Read into case cooling your best bet is to have a SIDE panel fan that is large like 120mm or more and running slow. It will force air at the chipset and ram plus give cpu and video fresh air to use. Makes a HUGE difference in all temperatures. These passive heat sinks are made for impinging air flow of which there is NONE in most cases without a fan on side (how could it, the air has to blast AT the sink not just by it).
Full feature used to mean hot running chipset but not AMDs I can tell you that. ITs got a ton of features and way less heat. Reason is it is a 65nm chipset Nvidia are what 130nm? Newest is 90nm I think on nvidia. Even the AMD 4 slot crossfire chipset isnt that hot. This 770 (single pci-e 2)is the lowest wattage of them all. In games it gets near 30c I seen it hit 32c once. My nvidia chip (NB and SB in one) on biostar T550 ran 32c idle! Nvidia chips are hot.