30 degrees C? That's pretty good. My Athlon T-bird 800 was topping out at close to 50 degrees C two years ago when I ran the machine with the sides on. Now it has other problems, but it still runs decently some of the time.

I don't know if I would want to build my own USB enclosures when I can buy a Network Attached Storage device that has 1 TB of storage for about $250, or my own fileserver for about the same price.