The inside of the chassis does heat up to about 50C after about 2 hours @nicoch58, but it seems to be stable after that so I don't know that I need to worry too much about it. If internal heat buildup does become a problem there is room for a small exhaust fan or two on the top cover. I have had it running for over 12 hours at a time while I was burning it in and the ambient temp was around 28C which is about as hot as my house ever gets. In the long run having the case run that hot is not going to be great for the electrolytics but I don't think I need to worry too much about that for 10 or 15 years. One thing that seems likely is that I will build myself a separate power supply box just for working with these First Watt amplifiers - I plan on building more of them for sure.
Also @Borats Baby those look very cool! Are those ACAs? Love the look.
Also @Borats Baby those look very cool! Are those ACAs? Love the look.