First, I want to state that if you have posted any builds or look at any builds as a guide, you've become part of this builders community. Constructive criticism can be helpful, so please, no down-votes without some explanation.
I've been wanting to build an HTPC-like desktop for some time, so I took this opportunity when a friend said they were looking for a new computer for general use. I was expecting that working in the smaller space would be more difficult than it actually was. Two of these parts were recycled from upgrades done to my own desktop, the CPU and the 2TB drive. I listed the price of these parts for what I paid (a year ago), not for the price I sold them. I tested how easy it would be to fit a GPU borrowing my own GTX750, but that is not actually part of this build, I did upload a photo with it for reference, because it was a bit tricky to work with the front USB 3.0 cable connected. Also, the 19" HDTV is only there for size reference. Now, on to the details in order of assembly.
Case: I've had my eye on this case for some time, and it turned out to be mostly what I was looking for. It is a bit bigger than I had expected, but still quite small (I believe smallest available fitting a dual slot GPU, ODD, and internal PSU). If you use the stock Intel cooler, then you can install the motherboard before the CPU. With most any 3rd party CPU coolers, then install that on the mainboard before installing the board into the case. With the motherboard in and front case wiring connected, I routed the cables as best out of the way that I could, and still leave a bit of slack to remove the front clip enough to get to the filter. Since I didn't install a 2.5" drive, I used that bay to run the SATA data cables. There is a bit of extra overhead clearance for certain slightly larger 3rd party CPU coolers. I could probably fit a 12cm low profile cooler in here. I do feel there is some wasted space in this case, but it does have good airflow. The included 12cm fan runs pretty quite, about the same volume as the CPU cooler. Overall; for $40, this is a good little case that's not too difficult to work in.
Motherboard: this one was the second cheapest available (at the time) LGA1150 m-ITX with WiFi, and the cheapest that featured an mSATA port. I think the orange LED "underglow" is unimportant, as it mostly can't bee seen outside of the case. There are some interesting features and drawbacks of this board. I believe this is the only board under $100 with a DAC USB. It has both a 50mm mSATA and half-mini PCIe (with WiFi AC/BT card pre-installed). It also has a full array of rear audio outputs. Some of the downsides include, only one SATA3 port, no display port, and some of the case connection pins may be awkwardly located (depending on your case, for me the front HD audio was almost a stretch). Overall, I think it has some great features for the price.
CPU: this is just a bit underpowered for an i3, but I sold it for the price of a cheaper Pentium, and the person is OK with that. It is faster than what they were expecting from it. I used some leftover Noctua thermal paste, since the cooler needed to be removed. It is very energy efficient.
RAM: I was originally looking at the cheapest 2x2GB memory, but i decided to spend the extra few dollars for the improved CAS latency of this set.
SDD: This is a very cheap 128GB, with good reviews. The buyer had never had a computer with an SSD, so they were quite impressed with the speed.
ODD: Simply the cheapest available that would fit this case. It did require a SlimSATA adapter. From this building experience, i would recommend going for one that is a flexible cable, like this one: http://www.amazon.com/StarTech-6-Inch-Slimline-Adapter-SLSATAADAP6/dp/B009JXKQ9O/?ie=UTF8 It was a bit too tight a fit with the fixed adapter. The power cable was the issue, as you can see in the photo. 1mm less space, and I would've had to buy the different one.
HDD: This person is an amateur photographer, so capacity was somewhat important. When I told them I had a spare, excellent condition, 2TB drive that i would sell for half new price, they were thrilled.
PSU: This is the cheapest 80+ SFX PSU. I've had good experience with FPS Group, so I trust that brand. This is a non-modular PSU. Combined with a small case made for the most challenging task in assembly. However, there was enough space too tuck most of the excess wiring out of the way. The biggest eyesore being the 24pin cable, but there isn't much else that can be done with that. This PSU can easily handle the added load of a GTX750 (and likely a 750ti, also). Unless, you need more power, or are exceptionally picky about excess wiring, then don't bother paying more than twice as much for a modular SFX PSU... at least not with this case.
Keyboard: This is a good little wireless keyboard with built in touchpad. It's compact, lightweight, and easy to use. The only slight drawback, is a lack of backlight. However, it's cheap and energy efficient. I do not recommend this for gaming use, unless you're the type that is comfortable gaming on a laptop keyboard and touchpad.
Additional notes: The peak power draw, as measured from the outlet, is 77.7W. this is running prime95 and Furmark for a full stress test. It was running an normal active average of about 40W. I did not run gaming benchmarks, as this is not a gaming PC.
Anyone looking for an easily upgradeable small form PC, then i would recommend looking at some of these parts to start out. I welcome any questions, advice, and suggestions.