100% CPU Usage is not necessarily a bad thing. Your mobo probably came with some temperature monitoring app, go ahead and load it if you are worried about temp.
Personally, I went nuts with cooling for my main machine. I have not had a hardware related crash or hang yet. I run a full tower case (Chieftec), with 3 80mm Antec fans in the front, two in the back, a 120mm in the back, plus an Enermax 465w power supply with a bottom and back fan. I run a P 2.53 with the stock fan, overclocked to 2.7. Without cutting holes in the case, or running water cool, this was really the most I could do.
After I built it in the office, my coworkers were laughing because if you passed a sheet of paper in front of it, it would pull to and stick to the front of the machine. Cool as a cucumber.
Oh, if you want to go that nuts, make sure the box is in a spot where the noise will get absorbed, and you use a charcoal filter right behind the face of the case. Otherwise you will be dusting once a month.
I think for my next machine, which I am about due for, I will go all aluminum. This will also lower the heat. I had an idea about using a 12v mini refrigerator and squeezing the guts of that into a full tower
We'll see what purchases I can make without the wife finding out