After 7 years, my old full-tower PC was starting to show its age and since I got a nice raise this year, I decided to treat myself. My priorities with this build were size/weight and noise control and performance, so I opted for the mATX form-factor.
CPU: Everything I've read indicates the 4790 is amazing and while I'm not planning on overclocking much, the 4.0GHz standard clock is pretty rad and seems worth the price.
CPU Cooler: As anticipated, the H5 was a breeze to install and barely required any assembly (backplate and cpu mounts were all thumbscrews). This came with Cryorig's CP9 thermal paste, which I've never used before, but I had some Arctic Silver 5 available, so I went with the known quantity.
Motherboard: I'm not planning on overclocking right away, but this was only a couple $ more than the same H97, supports 1866 RAM and gives me the option me to tool around a bit, in the future. The RAM slots are an adequate distance from the CPU slot so that there are no clearance issue with the H5. Asus' UEFI BIOS is really neat and easy to use as well.
Memory: I wanted RAM without giant heat spreaders, to ensure it'd fit underneath the cooler and I trust the brand.
Storage: SSD for the OS, with the 4TB hybrid for fast storage. I also decided to add an additional 2TB hybrid for exclusive use with my Steam directory.
Video Card: I was initially looking at a GTX970, but the 980Ti is a head and shoulders performance increase, which I felt justified the expense. I also liked that the I could get the card pre-OC'ed and this particular MSI came highly recommended. The card seems to run very cooly and the fans don't even spin up during normal desktop use.
Case: I knew I wanted a smaller form factor from the get-go (my old P182 was huge and weighed 30lbs for just the case) and a friend bought the Aerocool DS case before changing his mind and deciding to get something larger, and he sold it to me for half off. The horizontal motherboard mounting intrigued me and the case has good airflow, so I'm pretty sure it's a solid choice. I removed the ODD and 3.35" bays since they are unnecessary at this time and to head off any potential issues with the video card length. Cable management proved slightly more difficult than I had imagined, as there are very few discrete tie-down points in the case; I used velcro ties in most areas and duct-taped some of the less likely to be modified peripheral and fan cables directly to the chassis. This case comes with a replacement honeycomb top cover that has a dust filter built into it, but the front intake doesn't have any filtering for some reason, so I purchased a 200mm filter and stuck it beneath the front bezel.
Power Supply: Due to the smaller form factor, I wanted a fully modular PSU and I opted for a 650w, to give me some headroom in case I want to add a second video card in the future.
Case Fans: The case comes with a 200mm in the front, which seems adequate at this time, and I swapped out the 120mm exhaust in the back for a 140mm and added another 140mm intake on the top, for better airflow and quieter cooling. There's only three fan headers on the motherboard (one for the CPU cooler and two other PWM), so I ended up attaching the 200mm directly to the power supply; I may end up adding a discrete fan controller in the future.
Wireless Adapter: necessary, unfortunately, given the layout of my apartment but I wanted an internal card and this is the cheapest option I could find that can handle ac.