Based on the above, look into the benchmarks of the Nvidia 970/980 vs AMD 290's. If you plan on staying at 1440p, right now, Nvidia has the market cornered. Nothing wrong with AMD's, as I'm an AMD fanboy myself. However, the AMD's just don't really outperform the Nvidia's until you get into 4k resolutions. This tends to change every 2-3 years, with each company releasing a new architecture to one-up the other.
CPU-wise, Intel has the market and has dominated it for the past several years. AMD processors simply don't match their performance. Some fanboys here argue that under specific games and certain OS setups, the AMD's have a slight advantage - the fact they have to preface that should tell you everything you need to know. Intel has the larger market share, better board support, and better performance overall. AMD CPU's really only shine in terms of cost vs. performance.
Regarding processor differences within a manufacturer (e.g. Intel), keep in mind that CPU is usually the third factor in gaming performance, and rarely does an increase of 10-20% make a huge difference in games, unless you're maxing out your lane bandwidth. That is to say, most current generation and even previous generation processors are adequate for gaming. Go with whatever the latest generation is, but don't pay $200 for an extra 7-10% in performance, and don't hold off buying a current generation processor because the next generation is rumored to offer a 12% increase (an increase you'll undoubtedly also pay more for). Unless you're running something like Shadows of Mordor on Ultra Settings on a three-way 4k monitor setup (effectively 12k resolution), the differences between current gen and last-gen CPU's
typically isn't going to impact your performance much at all. There are exceptions, but keep this general rule in mind.
Look at the socket LGA1150 CPU's and motherboards.
Do some research and choose your video card and CPU (if you're building immediately, there's a 90% chance you'll go Nvidia+Intel), then pick a motherboard based on that combo. If you think you might SLI (run 2 or more cards together), then make sure the board supports SLI. If you go with an AMD video card, make sure your board supports crossfire. That is, if you plan or think you might run 2 or more cards.
Choosing your motherboard should be done based on your hardware and what it offers. Aesthetics are also something to keep in mind, if you plan on showing off your rig with a windowed case.
Don't forget about a sound card, if you want an aftermarket one. Most gaming motherboards have an integrated sound card, but if you're building a dream rig, you'll probably want a standalone.
You'll also want a hard drive. I prefer to install the main OS on an SSD (get a 256GB or larger), and then store larger files on a RAID of traditional platter drives. Add in a blue ray player / DVD drive, or two, and you should be set. Don't forget a wireless card if you plan on using WiFi (hard-wired is superior for gaming).
Windows 8.1 offers better gaming performance in most titles released over the last year. I'd go with that over Windows 7 (if you were considering it).
After you have these components, you'll need to select a power supply appropriate to your system. There's some handy power supply calculators. They're never 100% accurate, but they're good to use as general references.
http://powersupplycalculator.net/Pick out a case that suits your preferences, and make sure it has appropriate cooling. You can always add more fans. If you go into overclocking, you may want to look at watercooling. Corsair has some nice closed-loop stuff that is relatively affordable.
For your monitor, look here - it's the reference monitor to have for gamers pursuing 1440p and a 144hz refresh rate:
http://www.amazon.com/PG278Q-27-Inch-Screen-LED-Lit-Monitor/dp/B00MSOND8CJust use the above info for a primer, and then start looking at performance and benchmarks.
Remember, the things that matter most are:
- Video card
- Memory (RAM)
- CPU
In that order.
When it comes time to purchase, buy from Amazon if it's sold by Amazon.com if the price is comparable. They have a no-questions asked return policy. NewEgg is a close second, though note their return and exchange policies. DOA parts aren't the norm, but they are relatively common with PC's. It's much easier just returning to a place like Amazon than having to deal with an RMA policy.
You should be able to build a solid setup for $3k.
