Linus tested 3 GTX 970s vs 2 GTX 980s and found out that it is better to use 2 GTX 980s. Why? Because you won’t need to consume that much power with only 2 cards instead of 3 and the cards will not heat as crazy. Using three cards in SLI mode will result in the card that is positioned at the middle to heat up unnecessarily and make a ton of noise in return.
If you really have the money to spend buy one good, premium graphics card. The GTX 980 costs about $550 and the GTX 970 costs $330. Both use GDDR5, have 4 GB of VRAM but the processor clock speed vary and also the CUDA processors.
All in all, the GTX 970 seems to be the better option cost-wise.
Now, let’s learn about the M.2 the port on the motherboard where you can insert your M.2 SSD. Newer SSD can be inserted in the M.2 slot and you will have a ton of connection speed because of this. You will not need any wires to connect this SSD to the motherboard so you got some increased write/read speeds.