I gotta say, when you buy two kits of dual channel memory sure, it would equal quad channel memory. But if you buy two dual channel it wouldn't be the same as buying one quad channel set. Memory in sets are tested as sets and I really hate it when people buy sets that will work together.. but shouldn't work together.
If your gonna be spending 2k on a build then go for a 780 or 780ti instead of Crossfire 280x. It will be more quiet, take up less space, and use less power, and you also have the option to add another one if for some insane reason a 780ti isn't powerful enough for you.
I really like that. I'd probably be better off with the R9-290x anyway. However I really want to stick with the Bitfenix if I can. I'm kinda partial to the way it looks. Would I be able to get away with using it with the 290 or is that a pipe dream.