PCI Express x16 slots

I want to get a new motherboard for a computer I'm building, and it says "1 x PCI Express x16 slot with PCIE Switch card or 2 x PCI Express Graphics slots for ATI CrossFire" What exactly does that mean?

http://www.chiefvalue.com/Product-_-ProductDetails.cv_-_item--13-157-102

Also, I'm planning on getting an Athlon 64 X2 5200 Processor since AMD recently cut it's prices. How do you think an Intel Processor around $219 would compare to it?

Thanks in advance.

 

http://shop3.outpost.com/product/4587977

Will this power supply work with the motherboard?
And can the motherboard support an Athlon 64 X2 5200 CPU?