Just read an interesting review of a PCIe card which accepts four flash blades: http://barefeats.com/hard210.html Intro from the article: "Our readers have been frustrated by the inability to get more than 1500MB/s from Samsung SM951 flash blades mounted in slots 3 and 4 of the 2009-2012 Mac Pro tower. The x16 slot 2 has not been a helpful -- until now. One of those frustrated readers turned us on to a new x16 PCIe M.2 carrier board by Amfeltec in Canada. We obtained a sample which we populated with four SM951s. After striping them (RAID 0), we ran our storage benchmarks."