nah man with that CPU your temps are about right. lol infact looking at your setup it's almost exactly like my old one. MSI board with 2400+ XP and 5700 graphics card with 80gb hard drive and 300w power supply is what I had for a while lol. When I had my case with the side panels off and stock heatsink I was at 64C. After doing my case modding I got it down to 40C Idle, 44C if it was a hot day. Other than that, if you don't have any case fans, or you do, but it's only one or two and stock heatin...your temp is about where it should be. I figured my chip was running a bit hotter than normal and it really isn't, those 2400+'s seem to be in the 50's if you don't have adequate cooling.
The main thing about an aftermarket heatsink is your load temps not so much idle temps. Like before I'd go from 54C to 61 or 62C at load, when I got my SLK-900A heatsink, 80mm vantec tornado, and AS5, the load temperatures would only go up 2 degrees opposed to before it'd go up, 5, 6, 7, even more degrees up on load. It's because the heatsink absorbs the heat much quicker. So don't forget about that if you do buy an aftermarket heatsink. Your Idle temps will be like 2-5C lower, but it's the load temps that it really keeps down. Makes it so the difference between idle and load is only like 2C instead of 5+ that's how it is for me anyway. Load temp never goes more than 2C above idle.