Ok, a little update here.
Received the new board this morning from a different supplier. First thing I did was check the serial number, which was when my heart sunk. It was almost identical to the one I have returned, like so:
xxxxxxxxxx48 - Old board
xxxxxxxxxx50 - New board
That was almost too close for comfort. What are the odds of getting such close serial numbers for the same item from 2 different suppliers ? Only other thing I can think of is that the serial numbers are actually batch numbers of some kind, but I have no way to verify that.
Anyway, Ive stuck the bare board in the case with absolute minimum hardware as usual. The bios version on the board was 1707. To my surprise it booted up first time with 4 sticks of ram inserted (Corsair Vengeance Pro, see below) and went straight to the bios setup as expected. A good sign so far then!
Next up was to bump the bios version to the latest one (2004) and then reboot; still everything works fine.
Next I've swapped out that ram for my favourite modules right now, which are G.Skill 2133. Again everything works just fine with all 4 sticks in there and XMP selected.
Last thing for now is a quick run of the latest version of memtest86. I stopped it short actually at around 95% of a full test run, and not a single error reported.
All the signs so far are positive then
The next plan is to do some more in depth testing with several memory sets, of which there are four in total, each comprising 4 sticks :
Corsair Vengeance Pro Series, 1866, Part No : CMY16GX3M2A1866C9 (4 x 8Gb)
Corsair Vengeance LP, 1600, Part No : CML8GX3M2A1600C9W (4 x 4Gb) - 1.35v
G.Skill Ripjaws, 2133, Part No : F3-2133C9D-16GXH (4 x 8Gb)
Kingston HyperX, 1600, Part No : KHX1600C9D3X2K2 (4 x 4Gb)
Early indications then are good so far.
Next part of the plan is to fully install the board together with the armor kit which I already had, and all of the intended hardware for the build, followed by more testing.
I'll be doing a full single test run of the Corsair and Kingston ram sets, followed by an overnight run of the G.Skill, which is the intended ram for this build.