Now I have several questions about all this. First, I was wondering if all the components are compatible. Second, am I getting the best for my money? And also, the motherboard has 3.0x16 PCIe slots, and I don't know if the 2.1x16 video card I chose will fit in this. I'm pretty satisfied with how I suspect this will perform, so if there is any way I can cut the cost of this, please let me know!
As for your questions, the board you've chosen has 3.0 slots but they do not work as such. The 3.0 slots on any board currently will not natively support PCI 3.0 unless you have an Ivy Bridge CPU in it. Those are Intel's next gen chips probs to be released sometime at the end of next year.
As for the PCI, the basics are that all PCI gens are backwards compatible, So yes, the PCI 2.1 will work.
Save yourself some money and buy a 6870 instead of that 6950 because when OCed 6870 can reach same performance and even better than a single 6950 plus 6870 scales the best when in CFX plus 6870 is cheaper.