+1 on the 2500k CPU. Unless your on a real budget and go AMD 955BE and overclock. Asus motherboard for sure. Asrock is actually amde by Asus, it's their budget line. As for the video card, Radeon 6950 2GB version is a great card. A little pricy approaching $300 but a great gaming card and 2GB to boot so it's future proof. It's a good value compared to the $600 super gaming cards we are used to. Otherwise a 6870 for under $200 is a best buy.
As for brands I prefer to stick with Gigabyte, Asus, XFX, etc... on video cards. I stay away from budget brands like powercolor, sapphire, diamond, etc... I've had my share of problems with these brands and usually stick to gigabyte or asus. XFX is overpriced based on warranty.
Also don't forget a quality powersupply. When in doubt an Antec TruePower with 5 year warranty is a great power supply. I've never seen one die in over 15 years. I owned a computer shop and stocked Antec exclusively so I've seen a lot of them in operation. I also recommend an aftermarket CPU cooler. Check frostytech.com and make a decision based on their reviews and what available where your ordering from.
Need a cheap case, I like the Zalman Z6 plus. Comes with all the fans, cable management, SSD slot, rotated HHD installation, all for around $60 or so. I don't see any difference between the Zalman and a $120 Antec.