|Seems you're correct. =( I went back in my BIOS and found a few mistakes I made. those 1333Hz maximums were about the memory chips in the slots, and how much the RAM sticks themselves could handle, not the motherboard.|
I went to crucial.com and it seems the only upgrades compatible with my memory are, indeed, 4GB sticks. So it would seem if I want 16 gigs, I'd need to get 4 x 4GB sticks.
I did manage to boot to BIOS with only one of the 8GB sticks inside, that's how I found out about the Hz max thing with the slots, but it still wouldn't boot up normally. I do beleive you're correct, and it seems I'll need to make another exchange!