As the owner of a GX620 SFF, I have confirmed that a G.SKILL PC6400 2x2gb kit is fully recognized and compatible.
The Sapphire 6570 low-profile fits perfectly and works well, and a Samsung 840 120gb SSD is fully recognized as SATA II. The system is Windows 8 64-bit compatible, and all drivers apart from the onboard video are furnished on the install disc.
