Clockwork Catz :
Btw it says it is dual channel, does that mean I HAVE to have two or four sticks of RAM or it just means it supports it?
No, you don't have to have 2 RAM modules. You will, however, lose the dual channel feature which makes RAM effectively twice as fast if you only use one module.
The actual clock frequencies are half of the speed advertised, i.e. 2400 would actually be running at 1200 but would appear to be running 2400
when the dual channel feature is enabled. Without the dual channel feature enabled you'll get the 1200 and there's no way to enable the dual channel feature with just one module.
http://www.hardwaresecrets.com/everything-you-need-to-know-about-the-dual-triple-and-quad-channel-memory-architectures/2/
So 2X4Gb@2133 is better than 1X8Gb that will actually be running at 1200 without the dual channel feature.