Amazon.com: OWC 16GB (2 x 8GB) PC8500 DDR3 ECC-R 1066MHz DIMMs Memory Compatible with Mac Pro Early 2009 & Late 2010 'Nehalem' & 'Westmere' Systems and Early 2009 Xserve. (OWC85MP3S8M16GK) : Everything Else
Kingston ValueRAM 16GB Kit (2x8GB) 240-Pin DDR3 SDRAM ECC Registered DDR3 1333 Server Memory Model (KVR1333D3D4R9SK2/16G) at Amazon.com
Apple 16GB 4x4GB 1866MHz DDR3 ECC Memory for "Trashcan" Mac Pro, PC Servers | eBay