The PCI razor cards are getting very popular, SP is putting them in all their Ultra Storage line of server. We manage to do some benchmarks on the 24 NVME Samsung PM1725. Oracle ZFS striped/raid pool with all 24 drives. We got 7.7GB/sec using CLI DD tool. The architecture of razor cards and NVME drives to PCI bus is explained very well in this doc https://www.supermicro.com/white_paper/white_paper_NVMe2.pdf. To get that type of performance on a Flame box in theory 2 or 3 NVME drives will deliver 6+6=12GB/sec sequential reads http://www.samsung.com/semiconductor/global/file/insight/2015/11/pm1725-ProdOverview-2015-0.pdf Where the NVME are really delivering the performance is in the IOPS not necessarily in higher bandwidth because of other variables like filesystem, pci bus, cpu, OS, block size, single/multithreaded,.... You get almost x7 (tested with fio-2.1.7 in the SP engineering lab) more IOPS than the traditional industry standards SSDs. Flame requires a single stream of playback so the NVME in practice 2-3 of those drives will deliver up to 12GB/sec. I also hear that Flame is multithreaded if you use stone+wire. However in practice using cli tools I have not see anything faster than 7.7GB/sec in all my testing.
To add to what Saker about not needing the LSI controller. If you manage to get 3 pci slots x8 available in you Flame box, i think in the Z840 the 3 slots x8 are used for the aja and nvidia cards but if there is another motherboard that can give you three more x8 slots u can add those NVME drives and i would strongly recommend ZFS you will get that 7.7GB/sec that i am talking about.