I wonder if it's the bios as I couldn't pass 4300 ( ~4290 was max as I remember ) on the same board using various memory kits. VCCIO/VCCSA are limited in all official versions and 2 earlier betas.
I wish to see the same benchable at ~4500 in dual channel but I doubt it's working like that.
Right now it's hard to find any competition for G.Skill. I have no idea why Corsair or some other brands are not even trying or their highest series are only in press releases but later no possible to buy.
While G.Skill is releasing 3200 13-13-13/ 3600 15-15-15 kits then Corsair is showing press releases of 3200-3400 CL16 in their Dominator series and still more expensive.