Sample builds updated. Most remain the same with a few tweaks here and there. If you can find one, the Pentium G2120 is still one of the best sub-$500 gaming build CPUs that together with a good discrete graphics card can offer excellent performance in most titles. For WoW (and most other MMOs) however, the i3 3220 is probably the wiser choice still.
The 3570k remains the go-to CPU for anyone looking to build a decent-to-awesome gaming rig. SSDs are becoming more popular for each month and today they are almost common place. If you are looking to build a gaming computer for $700+, at least consider getting one. My recommendations for graphics cards are as follows:
Budget picks: Radeon 7770, Radeon 7850, nVidia GTX 460
Mid-range: Radeon 7870, Radeon 7950, nVidia GTX 660
High-end: Radeon 7970 GHz Edition, nVidia GTX 660 Ti, nVidia GTX 670
The latest drivers fixed some issues with CrossFire, but due to micro-stuttering nVidia is still the way to go for multi-GPU setups. As always, never pick two graphics card if you can achieve close to the same performance with one for roughly the same price.