As you probobly noted those require a pretty high voltage over standard 1.5v, did you use 1.85 or 1.95 as they require?
Suggest you start at setting voltage for 1.95 than clock to 667 with one set 2x2. See how stable that is then add second set. See how stable that is. I just looked at newegg spec for the board which says 1333 std and 1600 as an overclock.
The current processor certification was measured for 2 ram chips not 4 as you noted but I'm not aware of it as a megabyte limitation.
The internal memory controller in the Processor is based on 1333 with ddr3 but you can run higher but the gains are minimal, something like 2-3%.
If you can get all 4 chips going at 1.95v then you can try backing down to 1.85 and see how that works.
A last note if you use the default settings for the ram and then boot usually you can see a EPP clock enable and EPP voltage enable setting available in the bios with the gigabyte boards. This entry will not be visible if you use manual settings which is why I said use system defaults and reboot.
Sorry looked one more time they say extreme suggesting the high performance is coded intel which means you may have to type in the 667clock 1.95v and the latencies for 1333.