HP 4 GB DDR3 SDRAM Memory Module - 4 GB (1 x 4 GB) - 1333MHz DDR3-1333/PC3-10600 - DDR3 SDRAM - 240-pin DIMM at Amazon.com
G.Skill Ripjaws X Series 16 GB (2 x 8 GB) 240-Pin SDRAM (PC3-12800) DDR3 1600 CL10-10-10-30 1.50V Dual Channel Desktop Memory Model F3-12800CL10D-16GBXL at Amazon.com
AddOn 32GB DDR3 SDRAM Memory Module at Amazon.com
Kingston ValueRAM 16GB Kit (2x8GB) 240-Pin DDR3 SDRAM ECC Registered DDR3 1333 Server Memory Model (KVR1333D3D4R9SK2/16G) at Amazon.com