Just bought a new machine: GTX 1070, 32G RAM, i7 6800k, SSDs etc.I have three drives, two SSDs and one mechanical. I have a folder on my SSD that is also duplicated on the HD. I tested the machine when I got home and it was flying. Couple days later, I was working on one of the clips in that same folder, and the computer was ridiculously slower. I couldn't understand why it was so slow all of a sudden, until I realized that that clip (with the same name) was on the duplicate folder on the HD.
Moral of this story: don't neglect those SSDs, they might be the most important part in the whole machine. People are always asking about graphic cards in this forum, and a good graphics card will undoubtedly make a big difference, but the SSDs make a HUGE difference. I had always heard that everywhere (including in this forum) but I'd never thought the improvement would be so dramatic.
So my recommendation: when building a new machine, prioritize the SSDs.