I used to have a big fascination with small form factor and power efficient PCs. Other than having Mac mini for a while, I didn't actually implement to much on homebuilt PC side, mostly due to cost. I've had a fairly small mATX case and used lower watt CPUs. For projects like HTPC, the tradeoffs made sense, but I don't have one of those any more and for my desktop, I'm back to a full size case and full powered components and large heat sink to go with it.