Hi everyone! I've a Mac Pro 5.1 which I plan to upgrade soon. I plan to upgrade the CPU to a W3690 and install 64 Gigs of ram. So my question is: Can I upgrade to 1600MHz or 1866MHz memory? I have access to either from a friend. I think my system will only work at 1333MHz, which is ok, but since the upgrade is a great deal, will either work ok?