I've been searching for an upgradeable machine to replace my 2007 iMac, and after looking at my options for about $700 with a prebuilt and seeing the inside of a Dell Inspiron 531 that had a generic power supply and a generic motherboard, I decided that I could do better and have more fun building my own. I think I fulfilled those two objectives.
CPU: Great price for what you get, with more cores and a higher speed than any i3. As a first time builder, seeing all of the perfectly straight and bendable little pins on my $120 square inch of silicon as I installed the CPU caused me to pull back 5 times before I finally mustered the courage to drop it in.
Motherboard: Good value for the money. It has an onboard power switch, SATA III, and USB 3, which is all I really need. The only problems were that the southbridge cover was pretty beat up, the I/O panel didn't fit the board great, and the audio header may or may not be dead.
RAM: I got a good deal on this RAM at Micro Center, and it seems to be well liked. It's been working great, not much to say other than that.
Storage: I was planning on buying a WD Blue, but then I remembered that the hard drive that failed in my iMac was a WD Blue. We'll see how the Toshiba does.
Video card: It can handle Garry's Mod at 300 FPS, and it handles maxed out Mirror's Edge very well. I haven't played much outside of that, but I love this card so far. Nice and small too.
Wireless: I got this from the same Inspiron mentioned above. It seems to bottleneck the Internet speeds when placed on the back, so it's sticking up from the top of my case until I find a solution. The problem may be the wall, but it operated fine next to a wall for years.
Case: I love the side window, the fans (2 LED and 3 normal), and the design. Great for a sub-$50 case. However, one of the case USB 3 ports is bent.
Power supply: Corsairs seem to be well liked, and this one had the right wattage and the right price.
Optical drive: It's a simple OEM drive. I like the lack of a logo on the front and the price.
OS: I'm not a fan of the start menu, but I downloaded Start Menu 8 and all is well.
I picked all of these up at Micro Center. I wandered in to look at some parts and cases, and I left with a full computer. I guess that happens when a geek goes into a Micro Center, having only seen Best Buy all his life. Overall, I really enjoyed researching and building the computer. It's nice to gaze in the side window while a game is loading and think, "I built that".
Note on cable management: It's pretty bad. Does anybody have any ideas as to how to get rid of the thick cord bundle over the power supply? It's USB and fan power, mostly.