Your motherboard is probably the problem, as it is not designed for the power consumption of the 6950. Although it will be a pain, I recommend upgrading your mobo.
Looks badass apart from the RAM. If you're not planning on upgrading to 2x8GB in the future, get 2x4. This means the RAM will operate at dual channel speed (double the speed of one 8GB stick)
If you're doing a 980 2-way SLI setup, I would definitely recommend a higher wattage PSU. a single 980 would run fine on 650w, but in 2 way SLI a little more wattage is needed. Go for a 750w PSU at the very least. All your other component choices are compatible with eachother :)
In terms of GPU shopping, you will be bombarded with (mostly unintentional) misinformation. I know linus tech tips said that first, but it's true.
The GTX 750 Ti is still a very relevant card and will run most of today's big titles like GTA 5 and Crysis 3, however some lowered graphics settings...
I would like to know when the cooler master rs-500-asab-l3 came out. Release dates make the product's age blatant which is a helpful factor in determining whether the product is still good to use. thanks
I found a Cooler master PSU from 2006 and it still supplies just enough power to every component, and it even features PCIe power connectors, so it must have been REALLY high end. Surprising, as it was in a old dell dimension 5200.