ASUS M4A785D-M PRO
But those lists aren't useful. They list what memory and what cpu is supproted, sure, but not which memory is supported with what cpu.
Anyway I've accepted the offer, and I'll figure out the answer to my question next week. I'll simply see if I can select a slower speed in the bios and boot
and if not I'll order 2x4gb memory and problem solved.