System Usage from Most to Least Important: Gaming, internet
Parts Not Required: keyboard, mouse, monitor, speakers, OS
Preferred Website(s) for Parts: newegg.com
Parts Preferences: nvidia, intel
SLI or Crossfire: No
Monitor Resolution: 1920x1080
Additional Comments: First time ever building a pc (been using macs for years) so pretty clueless as to what parts are good. Looking to build something that will be able to run upcoming games well, such as Diablo 3 and Guild Wars 2 (mostly guild wars 2)
Since you are not overclocking, get the i5 2400.
For motherboard, get an asrock extreme3 gen3 for future proof reasons.
For graphics card, get the 560 ti.
For power supply, get an antec earthwatts 550w.
For hard drive get the wd caviar blue 500gb.
1) If you can find the extra $40 in your budget, I strongly recommend the i5-2500k over the i5-2400. Even if you don't want to overclock now, the chip is almost painfully easy to OC (like, literally, change a number on the BIOS screen), and it'll give your system a lot of additional oomph for a relatively small investment. You can pick up a nice $30 aftermarket heatsink sometime down the road when you do decide to overclock.
2) At your budget, you can definitely fit in a ~90GB solid state drive like the OCZ Vertex 3 90GB. If you go this route, you can put your OS and games on the SSD and get really snappy response times when booting/loading.
2) Hard drive prices are really high right now because of flooding in Thailand. if you have an old 3.5" hard drive from a previous computer, you may want to reuse that and hold off on buying a new one for a few months. If not, no big deal.
4) You have options as far as the case is concerned. The HAF 922 is great and will fit all your components with no trouble, but if you want to skim a few bucks, just make sure you find a decent case that can fit long video cards.