Here's the writeup I alluded to in my original post...
This build was somewhat of an exercise in not thinking things through and going over budget. My original goal was: a new HTPC that is as small, quiet, and low-power as possible. Specifically, I use MythTV on Linux as a HTPC platform. I thought I could do everything with an Intel Sandy Bridge CPU, given their low power consumption and high performance.
My original plans were:
CPU: Intel i3-2100 -OR- Intel i5-2500k
MB: Biostar TH61
Case: Apex MI-008
GPU: Built-in Intel HD 2000 or HD 3000
CPU Heatsink: Stock, then Noctua NH-U9B SE2
PSU and RAM: same as final
First problem: I chose the i5-2500k, not for overclocking, but for the HD 3000 graphics. For HTPC, HD 2k vs 3k theoretically shouldn't make a difference, but MythTV uses OpenGL for some stuff, and the HD 3k should defnitely be better for 3D applications. That in mind, perhaps the i3-2105 is the best CPU, but I was buying from Microcenter, and they don't carry that chip.
Because I went with the faster/4-core CPU, I found that the stock cooler was too loud (I suppose it could also be too loud for a lesser CPU). My choices for a CPU cooler in this situation are very limited: basically, I needed something that's no wider than the socket itself, given its proxmity to the PCIe slot. (Note that my original plans didn't call for a GPU, but I was thinking of maybe using a Broadcom Crystal HD card, so I wanted to keep the PCIe slot unobstructed.)
I couldn't find anything that suited my needs, although in hindsite I think the Thermalright AXP-140 would have worked. So I went with the Noctua NH-U9B SE2, which was too tall for the Apex MI-008 case.
So now onto the second problem. The MI-008 case was too short for the new Noctua heatsink. The other problem was the lack of any case fan. In this site's review of the case, it was noted that a 120mm fan could be wedged into the side of the case. Unfortunately, this can't be done with a picoPSU on a motherboard whose power connector is right on the edge (technically, it might be possible, but to me it felt like the fan would put too much pressure on the solder points of the picoPSU).
I ordered the Lian Li PC-Q11B to replace the MI-008. (I was already familiar with this case because I used it for a new PC build for my parents.)
Now it looked as though everything would be just fine, but I found out that Sandy Bridge graphics support on Linux is "bleeding edge". These days, I don't have too much time to mess with getting the software to work; not to mention the poor WAF (wife acceptace factor) of having an unstable HTPC. I wanted something that should "just work". SNB graphics on Linux can be done, and I started to go down that road, but it required too much tinkering to make it work, so I scrapped the idea.
The easiest and most common solution for HTPC graphics on Linux is nvidia, and right now the GT 430 seems to be the GPU to get for this purpose. Of course I wanted it silent, so I bought a passive GPU, specifically the Zotac. That brought on another problem: I didn't notice that the GPU heatsink wrapped around the back of the card, causing it to interfere with the Noctua CPU heatsink! So I ditched the Noctua in favor of the Thermalright (after seeing
josephclemente's nice Q11B build).
Later, I saw on Newegg that Asus makes a passive GT 430 card that (at least from their picture) looks like it wouldn't occupy more than one slot's space---meaning it might have actually fit in the Apex MI-008 that I originally wanted to use!
The next problem was power consumption of the Biostar TH61 motherboard. Initially, when I planned the build, I wanted to use the Intel DH67CF, as anecdotally, Intel motherboards have the lowest power consumption. However, the Intel boards have a significant price premium. Ironically enough, I initially wanted to keep this build in the semi-budget realm, so I opted for the cheapest mini-ITX board that met my requirements, which was the Biostar. I was really disappointed in the power consumption though: 28 Watts at idle with the i5-2500k, 8 GB of RAM, SSD hard drive and picoPSU. With the picoPSU, I was really hoping for less than 25 Watts. Normally I wouldn't quibble over a few watts, but at this point, I was getting so frustrated with all my mis-steps that I decided to go ahead and send back the Biostar and get the Intel that I wanted in the first place.
And then I found out the hard way that the DH67CF has a huge chip on the back of the motherboard which interferes with the mounting bracket of the AXP-140. I posted about this
here. Again I drew inspiration from josephclemente's build, and opted for the Asrock H67ITX motherboard.
At the end of the day, I wasted a lot of money: I over-bought on the processor (i3-2100 would have been fine), I ate shipping and restocking fees for two motherboards, I ate shipping fees on the case return, and right now the Noctua heatsink is sitting unused (although I do plan to use it for a future build).
If I were to start fresh with the experience I now have, I would have used the i3-2100 (or i3-2105) CPU, Thermalright AXP-140 heatsink, Asus passive GT 430, probably the Asrock H67ITX motherboard, and made the MI-008 case work (by making neccessary modifications to fit a case fan in there).
Things can be tricky sometimes.