That is GDDR5 not DDR5. PC's are only at DDR3.
Now i'll let it out.
1) 32 GB sticks are only on the Server Side plus they cost around 1000 USD each. Regular DDR3 only goes to 8GB sicks and even then the high end boards support 64 at most unless you get like the SR-X which is a Dual Xeon board which support 96GB of ram but those are discontinued.
2) Nvidia Crossfire?? No No No. Nvidia has SLI, AMD has Crossfire.
3) IF you want 4 Graphics cards to at 16x each you will need a Dual Xeon board. Even then I don't think they can run at 16x each. I think they run at 8x Each. besides most graphics cards can't even use all the bandwith that a 8x PCIe 3.0 offer unless its some Dual GPU card like the new R9 295X or the Titian Z or something crazy as hell.
It sounds like to me you really need to read up on hardware first before you start building a monster of a machine like this.
Also you better have at least $5000-8000 USD for what you want to build as well.