I'm going to build an i3 (530/540) or i5 (750) HTPC system which will be used mostly for watch Full HD movies, hearing lossless music (attached to Onkyo-607 receiver) and playing a low/mid level graphic games.
I'd like to find the optimal heatsink + fan (low profile) which will fit an HTPC case (if you can write me the case's model it will even be better) which will be as silent as it can be (water cooling is not an option) and will spread the hot tempratures as best as it can be.
I was looking for many hours for the optimal solution in this site, at frostytech.com, quietpc.com etc ... but haven't find the best solution yet.
Your choice in case is going to decide everything. Most of the m-itx HTPC cases are not gonna allow you anything much bigger than a stock heatsink/fan. On the other hand something like the Coolermaster 360 gives you alot of room for aftermarket fans. The bigger the fan the more air it moves at a lower rpm and usually the quiter it is. You can fit a h50 closed loop in a Coolermaster 360 also any heatsink under 110 mm or 4.5 inches should also fit in the case.