G.SKILL Ares Series 16GB (2 x 8GB) 240-Pin DDR3 SDRAM DDR3 2400 (PC3 19200) Desktop Memory Model F3-2400C11D-16GAB at Amazon.com
48GB (3X 16GB) Matched Pair 1333MHz 240-Pin SDRAM DIMM DDR3 (PC10600) Memory Upgrade Kit for PC Desktops, Mac Pro 'Nehalem' & 'Westmere' (OWC1333D3X9M048) at Amazon.com
Corsair CMZ16GX3M4A1600C9B Vengeance Blue 16 GB DDR3 SDRAM Dual Channel Memory Kit 1.5V at Amazon.com