Okay,

Which DDR3 is the RAM ? DDR3-XXXX ?
"Western Digital 320GB" could be anything on the Market.

Unless you use PCIE Riser Cables, you cant Add all 4 Cards to the Board, due they Are Dual Slot.
You can Add 3 then, cause the 2nd Card will hide the 3rd Slot.
Power should be enough when you downclock the Memory.

CPU is on Komp list of the Board, so should work.

Greetings, Frog