Well then , it seems like you are actually getting serious about gaming. A an I7 2600 is a nice CPU.
With that in mind If we say 300$ total, then I would go with something like this
http://www.newegg.com/Product/Product.aspx?Item=N82E16817207014 (XFX unit made by seasonic who happens to make corsairs as well and a few others ) and
attach it to something like this
Now if you are gonna be extreme and think of the power supply as a *need* (because it is the single most important component when building a gaming PC )
Would be my next recommendation.
As BZ said, Corsair , enermax, PC power and cooling , XFX , Seasonic are all fanstic PSU manufacturers.
I5 3570K@4~5.0ghz: Gigabyte GA-Z77X-UD3H:Corsair Hydro H110 :16GB Corsair Vengeance DDR-3 1600: x2 XFX Radeon 7950 @ 1100/1575 : Corsair AX 860 PSU: x1 WD Black 1TB HDD's: 90GB Agility 3: 960GB SSD : Creative Labs X-FI:Corsair 500R Arctic White Edition:3 22inch Monitors Eyefinity @ 5294x 1050 : Alienware Tact-X Keyboard: Razer Naga :Corsair Vengence 1500 Headset: Corsair SP2500 Speakers