Looks like a really nice build. Since you're getting a K-Series processor, you might want to make sure you look into getting an after-market CPU cooler so you can overclock as high as you really want. I recommend the Cooler Master Hyper 212 Plus, Cooler Master Hyper 212 EVO, or NZXT Havik 120. I would have recommended the Havik 140, but it might be a little tall for your case. I can also strongly recommend an SSD to use as your boot drive, but that might not fit into your budget once you factor in the CPU cooler.
He doesn't need the 3570K (although I love it). The 2500K will be fine for gaming and a bit of video editing. But as you say, their price is pretty similar if you want to go that route. The 2500K is better for overclocking, though (SandyBridge generally better than IvyBridge in this regard).