Go with the 2GB 6950 - with a BIOS flash it will perform at the exact same level as the 6970 and it will save you $50 - $60. This would be a better choice:
GPU: Radeon HD 6970 2GB http://www.newegg.com/Product/Prod [...] 6814150517
For RAM it doesn't really matter what brand you go with as long as it doesn't have tall heat sinks and is 1600MHz timing 9-9-9-24. Corsair, G.Skill, PNY, Crucial, and Kingston are all generally good and reliable brands.
Case: How big? Do you need any partiular ports? What kind of looks? How many fans?
Mobo: If you want SSD caching, get an Asrock z68 extreme4, otherwise get asrock p67 extreme3 gen3.
HDD: Any reliable 7200 rpm drive will do, just get the cheapest one.