Yea that makes sense. So the 2400 ripjaw would be even better then the 1866?
Theoretically, except the AMD FX series CPUs have an IMC (Integrated Memory Controller) that is not stout enough to take advantage of the 2400 mhz RAM. The IMC would not be stable at that high of frequency. Trust me, the 1866 mhz RAM is what is appropriate for your CPU.
Also I'm noticing the same things with video cards
Things like core clock 1020mhz etc...
Don't confuse the processing frequency of the GPU with the video card's memory frequency. Two different things. Processing frequency = core clock. With discrete (meaning a separate video card rather than onboard or APU graphics) GPUs, however, they can handle RAM with a very high frequency. Don't worry about all that too much. Worry more about the processing frequency of the GPU itself than that of the video card memory. Just get one with GDDR5 memory. Don't make this unnecessarily complicated for yourself. Further down the road it will make more sense to you as you have more do-it-yourself build experience.
One thing you never stated is budgetary restraints. If there are none then there are more powerful video cards available than the Radeon 280X but if money is at least somewhat an issue then it's a good bet.
It makes it very hard to choose.