My old PC was running an older 4000 series AMD card which was definitely showing it's age, mostly with the fact that it did not support direct X11. Shadow of Mordor finally pushed me to the upgrade.
I'm going to be primarly gaming (modded Skyrim, Shadow of Mordor, Battlefield 4) and then my girlfriend also uses it for school.
I ordered all parts off of Amazon just because the free 2 day shipping with Prime. Spent a little bit more on some parts but ultimately the lack of patience for shipping paid off for me.
CPU: After reading review after review I finally decided on the 4690K which fit into my budget and has the chops to run the games I want. I've never tried OC'ing but it's something I definitely am going to get into which is why I went for the K.
CPU Cooler: Wanted water cooling and this one fit into what I wanted to spend and had pretty good reviews.
Motherboard: I really had no idea what to look for in a mother board other than I wanted the Z97 for OC purposes. Reviews and price on this one seemed pretty good so I pulled the trigger.
Ram: I know what ram does and the different speeds but brands I don't know the good from the bad, after looking around these had the best price, look, and reviews.
SSD: I've only heard of the dream that an SSD can be in a PC. I now understand that. I use it for the OS and the games that I invest the most time in. From a cold boot it takes 12 seconds for it to be ready for anything, Skyrim loading screens allow me to read 2 words before it's back to the action.
HDD: Looked at reviews and price and this fit into it.
Video Card: Obviously as I stated before I needed one that supported DirectX11, this of course does that. The card is a dream compared to what I had before! Everything I throw at it so far is 60 fps in 1080p. Wanted a PS4 but now I don't see myself going to one anytime soon.
Case: I really really wanted a Fractal R4 but they didn't have it prime and without prime it was about a 3 week wait for it to even ship, how about no. After countless hours reading reviews I finally decided on the Phantom 530. I love this case, it is sleek and looks amazing and had very good cable management options. I will probably never stray away from a full tower again.
Monitor: I bought the first one about two years ago and then the second one a year later so I'm guessing the prices. The only issue I've had with them is they do not have a DVI port which my GPU needed since I was using the only HDMI slot on it.
Keyboard: I just got yesterday from Wal-Mart so it was more expensive than buying it online but I needed it right away and couldn't wait for shipping. So far it's been amazing, the back lit mechanical keys are uber responsive. On the plus side it goes perfect with the Naga.
Mouse: The mouse I also bought two years ago, after using it I will never be able to go back to a mouse without the extra buttons.