RE: Dell XPS 13 2015 and Samsung 950 PRO m2 Upgrade
I was planning to buy one of those cards myself, however I found the some conflicting information.
So I have been researching this for a while, although it seems the 9343 will not support the PCIe (NVMe) ssd's as it seems to be only SATA (6Gbps / AHCI) in the manual.
The 9350 has support for the PCIe (8 Gbps / NVMe and SATA/AHCI).
Now I am not sure a BIOS update would change this, the M.2 basically supports SATA and PCIe connections but could be limited to 2 lanes PCIe.
So the XP941 from what I could gather is a OEM version of a 840 evo, the SM951 could be a 850 evo but I am not 100% sure if that is a correct assesment and how accurate this is from what I have read, the SM951 is newer but the drives are fairly similar although I think the XP941 is only PCIe. http://www.tomshardware.com/reviews/samsung-sm951-m.2-pcie-ssd,4045.html
Although you have 2 versions of the SM951 a PCIe (NVMe) and a SATA (AHCI) drive and you can guess the latter is slower but will work in the 9343.
Hope this explains a bit, but it seems the 950 Pro will not work in the 9343 (gutted )