which could enable up to 64GB of system memory to be installed in a quad-channel configuration.

Quad-channel configuration? It'd be interesting to see how much data that can push, and whether it's overkill unless you've got a pair of SSDs in RAID 0.

8GB modules are expensive because they're still pretty rare. 4GB modules are as low as $30-35 if you're buying them two or three at a time. I wouldn't buy 8GB modules until they're in a similar price range. If I was going to spend thousands of dollars just to run WoW, I'd get a RevoDrive instead.