Either system will 5-box without issues.

I'd personally like more then 6GB of ram, and would get a 12GB system.
You won't need more then 6GB for warcraft, but 12GB gets you some overhead.

I'd probably go with an i7 920, and overclock it if you wanted more performance.
Don't think the faster processors are really worth the cost, but that's up to you.

What will you be putting on the SSD?
80GB should be plenty for your OS and Warcraft.
Do you need the extra 80GB for something?
Is the 160GB faster than the 80GB?

Will you be exclusively warcrafting on the system?
Or will you use it for other games too?
Warcraft generally doesn't like SLI/Crossfire, but you can probably disable that for wow and enable it for other games.

Just some thoughts.