No, there is nothing wrong with SiS. It's just that every compant has their hits and misses, and with the major players like Intel or Via more people buy their stuff, and if a product is flawed you're more likely to hear about it and avoid it. Of course all of this goes out the window if the nieche product is better, faster, or substantially cheaper
I have built a htpc with the Aria case and an Abit VA-10 mainboard mainly because I had an Athlon XP 1800 and matching RAM at hand. Unfortunately it runs a lot hotter than in its previous home, a minitower case. Current idle temp is 68 deg. (The idea was to have a case that integrates in a hifi rack)
I also have a P4/2.53 running in the same room at the moment. It's another 30 degree day in my sourth facing apartment, and the P4 idles at 51 degrees. I have reason to believe it would be reaching 60-65 in the confines of the Aria case as well.
As to why, I can only speculate. Hot air rises, and in the midi tower it gets blown out by the case fan or the ps fan, or warms up the top of the metal case (acting as a heat sink) With the Aria, the top is plastic, and there is no direct path for the air to stream out. I figure the engineers forgot to have holes cut in the back of the power supply where the single fan resides.
I think the Aria is unsuitable for anything that puts out more than 50W. Shuttle has a much better design with a heat pipe transporting heat to an exhaust fan, but of course no way to fit in two TV tuner cards, which is what I was looking for here.
I have not had a chance to play with Cool&Quiet, in theory with 22w idle it should be fine. Looking forward to your report