Built this as a downsized version of my Heliotrope. The Corsair 400R case was awesome, but too huge, and since it had to live on the floor it always got dusty fast. This little Rosewill U3 case fits easily on my desk and has a window to show off the components. I use it for moderate gaming, web surfing, and general office work. See the original post for part comments, those below are only the new pieces. Thanks!
CPU Cooler: Chose this one since my case has only 1 fan, wanted something that could keep a lot of air moving. It's also one of the best looking coolers out there, and since it gets to be front and centre in the window it had to look good! (Goodbye, Hyper212 Evo) I guessed a SFX PSU would be needed with the size of this cooler, and I'm glad I did. A full sized ATX PSU would have conflicted by about 5mm. Clearance from the HyperX RAM to the bottom fin of the cooler is about 1-2 mm, and there's room to install all 4 sticks with no conflict. Gorgeous cooler, nice quality, quieter than my "quiet" case fan even at full RPM. Heavy though!
Mobo: It's the only 970 chipset mATX AMD board. ASRock's tuning utility has been excellent at tweaking system settings (particularly the fans), and even auto configured my RAM at 1866 despite that being an "overclocked" speed for this board. Some of the back USB ports feel a little loose, but they work.
Case: I love love love this little case. It's well constructed, light, and comes with every little part you might want. There are some kooky things though. The motherboard mounts only accommodate 5 of the 8 mATX mounting points, and plastic props are given for the remaining 3. There is about 1.25 cm of space behind the mounted motherboard for routing cables, useful with a little pre-planning. The front USB3.0 and audio headers' wiring can interfere with graphics card install if you have a longer card (mine only barely fit), and the USB3.0 cable could be about 2cm longer for my board so it could be hidden along the bottom of the case window. The perforated case edges along the front of the openable side can be used as tie points for cable organization, if your cables reach that far. There's enough clearance between the window and the raised bottom edge of the case to sandwich a SSD or two in there against the glass if you're not into the given mounting points. I'm planning to rig in a 2.5" bay like the U2 has inside the front wall of the case. There is only one dust filter, and it's screwed on behind the only case fan.
Case fan: I grabbed a Corsair quiet fan since I'd heard the stock case fan could be noisy. This one makes a whining sort of sound when it gets above 900 RPM, very irritating. With the ASRock tuner I can set it to lower capacity but unimpressed with needing to do that on a $20 case fan. Looking at swapping to a Noctua or something.
Temps are a bit higher than they were in my ATX build but still very reasonable. I've currently got the CPU cooler and case fan pulling air in from the back, while the PSU and GPU are exhausting out the back. I might flip the cooler and see how it goes, but the cooler install was difficult in the tight case with PSU installed so not looking forward to that one.