If you want to waste $380 on RAM then by all means it's your money, but you could upgrade your 6970 to a 6990 or 2x 6970 by getting 8gb now and 8gb later, and I guarantee you won't notice any difference between 8gb and 32gb in a gaming system. But you will notice a significant difference between a 6970 and 6990, or 2x 6970 in crossfire.
Also, the motherboard you picked won't run dual graphics cards very well, it only has 16x/4x PCIe lanes...not to mention it's a micro ATX board. You do realize you're putting a micro ATX board in a full tower case right?
You should take some more time to research mate