That is what I meant by cooling system. The heatsinks are the primary means of cooling and the new design they have been using in refurbs and warranty exchanges has an average of 10 - 15 degrees cooler.
jph - The newer boxes bought in the past few months will be of better build quality and could use the newer, cooler CPU. The GPU is the primary cause of overheating though. The only way to tell before you buy it is to check the wattage rating on the UPC sticker. I can’t remember off hand what the hi/low values for that is.