I have the MSI Z87-G45 board, added an other 2x4gig team group 2400 ram (already had 2x4gig) taking me up to 16gig.
To get it stable I had to down grade it to 1600 otherwise I was for ever BSOD.
Both sets run at 2400 if they are on there own, system just doesn't like it, though the sticks are very close to the CPU heatsink as the ram spreaders are huge so could be a heat issue at the higher frequencies.