One thing about heat is true. In summer, in Chicago, IL, it gets really hot. What I recommand is to see if you can find a much slower processor. I personally have a VIA C3 900 and 1G machines. Why? VIA 1G when powered up will only produce 18W of heat where else P3 of the same speed will make about 55W. That's a big number so if you are using the Celeron you may want to cool it down a little or make it open so that you have enough air circulating. Remember that your trunk gets hot as well.
Apart from that I think you have it set.