My Asus A88XM Plus based system unexpectedly stopped working and will not now boot. I see the MemOK LED is red and I'd like to try a new stick of memory. Currently the system has a single 8GB Kingston HyperX beast module clocked at 2133MHz. What is a cheap option for me to purchase to try if it is indeed the memory which is at fault? Do I need 2133MHz? 8GB? 4GB? 2GB?