Glad you found a MB that might do all the necessary work you will be wanting to get out of your computer build, Ramesis
below is something I meant to post for you the other day, and follows up on what Chalenge posted regarding a GPU running in a PCI-E X16 slot that has access to all 16 lanes, but drops to only 8 lanes ( X8) when another card or adapter is plugged into the 2nd X16 PCI-E X16 slot
PCI-E lane complications
Even this early in M.2 development, there are already M.2 drives like the Samsung XP941 that have read speeds that are twice as fast as any SATA-based SSD. However, there is a very finite number of PCI-E lanes in a system and a M.2 PCI-E drive will need to use a certain number of them. This means that instead of checking to make sure your motherboard has enough SATA ports, you instead have to check that you have enough PCI-E slots and lanes. Many motherboards have plenty of PCI-E x16 slots, but it becomes a problem when you realize that usually very few of those slots can actually run at x16 speeds.
Asus Z97-A PCI-E slots
For example, say you have a Asus Z97-A and want to install a M.2 x4 drive using a PCI-E adapter. That motherboard has two PCI-E x1 slots and three physical PCI-E x16 slots. The two PCI-E x1 slots don't have the necessary number of PCI-E lanes for a M.2 drive so they cannot be used. For the x16 slots, it turns out that the bottom PCI-E x16 slot is actually only capable of x2 speeds, so that slot will not allow for the full speed of a M.2 x4 drive. The primary x16 slot is likely needed for the GPU so it is also not available to be used. Finally, the second x16 slot is capable of x8 speeds so it will work for the M.2 x4 drive, but using that slot will actually reduce the primary slot (and thus the GPU) to x8 speeds. We've shown in the past that modern GPUs do not show any performance loss by running at x8 speeds, but it still is not ideal. And remember, this is just to add a single M.2 x4 drive and doesn't take into account other PCI-E devices you might have like sound cards or wireless cards. If you want to add a second M.2 x4 drive, you are pretty much out of luck until someone releases a M.2 to PCI-E adapter that can handle multiple drives in a single slot.
The PCI-E lane issue is less of a problem on X79 or Xeon E5 systems since the CPU (and thus the motherboard) has more PCI-E lanes available, but you still need to plan it out ahead of time to make sure you don't run into any surprises. Hopefully future Intel CPUs will add more PCI-E lanes to make this less of an issue, but for now this is the biggest limitation we see in terms of M.2 adoption
Refrenced Link for above quoted info:
https://www.pugetsystems.com/labs/articles/Overview-of-M-2-SSDs-586/#PCI-ElanecomplicationsRegarding picking out a M.2 Drive...
their are 5 common M.2 Drive Lengths for mounting and 2 types of M.2 sockets ( B key / M key )
ASUS has come out with the U.2 socket as well... check out the below link if you haven't already seen it or found it in your research
https://rog.asus.com/articles/hands-on/easy-guide-to-ssds-sata-msata-m-2-and-u-2/Hope the links and info I posted above help...
now my personal opinion/view from experiences:
as for Brands/Manufacturer and models of SSD, M.2, U.2, SATAIII etc... I prefer using Crucial over other Brands, I have yet to have one fail, unlike some I have replaced like OCZ, Plextor, Intel, Kingstonand a few others, while repairing/fixing other people's computer problems....
I've slowed down quite significantly on building new PC Builds and repairing them for others, over the past year or 2... and have not kept up on this stuff like I used to, but constantly working on and fixing other people's computerskinda knocks the wind out of the Sail, and drives one towards not even having the desire to turn on one's own personal computer, heh...
anyway...
Hope this helps
TC