And as for the GPU, I can't decide whether to go for the R9 290X, 290, or 280X... the resolution I'll be gaming at is 1680x1050
CPU: Intel Core i5-4670K 3.4GHz Quad-Core Processor ($254.99 @ NCIX)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler
Motherboard: ASRock Fatal1ty Z87 Killer ATX LGA1150 Motherboard ($129.99 @ NCIX)
Memory: Kingston HyperX 8GB (2 x 4GB) DDR3-1600 Memory ($95.30 @ NCIX)
Storage: Seagate Barracuda 2TB 3.5" 7200RPM Internal Hard Drive ($89.99 @ NCIX)
Case: Cooler Master Storm Stryker (White) ATX Full Tower Case ($179.98 @ NCIX)
Power Supply: EVGA SuperNOVA NEX750B BRONZE 750W 80+ Bronze Certified Semi-Modular ATX Power Supply ($79.99 @ NCIX)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer ($23.98 @ NCIX)
Do you ever plan to run Crossfire? If not you could save a few bucks and get a smaller power supply. For that resolution the 280X would work great. Whatever you end up picking make sure to get a non reference GPU with more than one fan. Those R9s get loud.
Do not get that PSU. It has a bunch of really low power 12V rails and can struggle to power most GPUs despite the wattage claims. It is crap.
You don't need anywhere near that much power either. 550 or 600 watts will be plenty.
All of those cards are very good. Although check out the GTX 770 and 780. On sale they can be had for similar prices and are incredibly good.
Just make sure to get a non reference card, especially when you buy the R9s. The 280X, 290 and 290X with the stock blower coolers sound like leaf blowers and run incredibly hot.
At 1680x1050, any of the GPUs will be fine. I would personally go fo a R9 280X or R9 290, and then pick up a nice 1920x1080 monitor. Use the 1680x1050 monitor as a secondary monitor for chats and stuff.
+1 on the reference R9 290/290X