GF's father was essentially looking for a Adobe PS/LR machine. Benchmarks seemed to call for a 4 physical core machine with high single threaded performance. 6600K seemed to fit the bill. GF chose the case, and they were adamant on a desktop-style case as he relies on the machine to elevate his monitor. Seeing no need to go any bigger, we considered one of Silverstone's SFF HTPC cases, though she chose the specific model.
The case has allowed us to fit everything he wanted, even an optical drive. It will also leave a half height PCIe slot for expansion, which may be a USB 3.1 Type C card in the future for his file transfer and possibly future photography peripherals. It was easy to work with and hardly the cramped headache people online were making it out to be. Yes, you have to be neat but everything fits even with a non-modular PSU without having to force anything with uncomfortable levels of force.
ASRock has been delivering boards at feature-parity with lower price for a few chipset generations now, and I went with the Z170M-ITX board. It fits our purposes perfectly, sans USB 3.1 support. ASRock does offer a gaming ITX Z170 with USB 3.1 but the premium wasn't warranted for us, especially as we would have the expandability there for us.
The new K chips don't come with coolers, and I chose a Noctua L9i to cool the CPU. I had hopes to break 4GHz with our form factor but that did not happen. We ended up with 1.17v and 3.8GHz. Although stock can push a single core up to 3.9 our configuration is a full-time 3.8 on even 4 cores under stress, so I suppose it counts as a mild OC. My cutoff is 85C under stress testing, and under daily use the temps are well controlled. One could conceivably push the clocks a bit more and still have the temperature headroom under 24/7 use, but a "true" 3.8 is what we settled for.
The case has a combo area that is either a slim ODD, 3.5" drive, a 120mm fan, or extra CPU space. If we didn't have to put a ODD in this system a larger sink could have been used.
The memory kit worked out of the packaging, no issues.
SSD and HDD are both old hat - well known parts and no issues.
The PSU was the letdown here. It is the noisiest part of the system. It is a very light sound and imperceptible from a few feet away in the noise environments I find common, but if it was dead silent ambient, it would be audible. It sets a baseline noise that did not want for this PC, but it's not a huge deal, mostly a matter of pride in my builds.
ODD is sometimes said to be problematic online, but we had no issues. Keep in mind you need a slim-SATA cable adapter if you are going to be building something similar. Silverstone makes one. Everything worked for us no issues.
I populated the 2x 80mm side fan positions with Noctua fans and Silverstone filters. It was partly a performance choice but also a choice for the bearing. As this will be gifted and I probably won't see it again I don't want the fans acting up and with these Noctuas I know I am not going to get a call a few years down the road about the fans breaking or starting to produce a noise. It also allowed us to run slightly higher RPM while keeping the noise down. The interior of the build is cramped. I'd definitely suggest populating both slots to get that air through and maintain positive pressure.
Overall this was a straightforward build with no problems. I can vouch for every part used except the PSU, but I am afraid there are few alternatives at the price for a SFX PSU.
Like other Noctua sinks it is quality and operates quietly, but unfortunately the cooling performance is merely par for the form factor and not significantly better than the competition while being more expensive. I chose this for the quality fan bearing building for someone else, so that they will not run into any issues for years and years, and that makes it worth the money. However, if just talking about performance, the price premium is not going to buy you any more cooling.
Bit noisier than expected.