Most people goes for SPV clients as opposed to full nodes. It should be rather fast (few hours) if you use a pretty new hardware. IIRC, Core 0.15.0 did have significant improvement in terms of the synchronization time. So did 0.13.0, 0.14.0.
I don't consider SPV safe, which is why I want to improve my full node experience as much as possible. Core has indeed gotten faster lately. In the early Bitcoin-QT, with this same computer im using now, it was a pain in the ass to run. Nowadays I can run it, the RAM usage is only about 500MB, but I would like a faster sync time and I guess a modern CPU will be a big improvement.
Intel. AMD is still lacking behind in terms of performance. If the application uses more cores effectively, then go for AMD.
I was betting on Ryzen but it seems Intel has won the battle again?
http://cpu.userbenchmark.com/Compare/Intel-Core-i7-8700K-vs-AMD-Ryzen-7-1700X/3937vs3915
The Ryzen got 2 more cores and 16 threads but im not sure if there are any programs were it would be worth it. Intel wins on every department it seems. I got some hobbies such as video editing and music but im not even sure if these extra cores would make much of a difference.
M.2 SSD is definitely faster than both SATA SSD and HDD. However, the cost would be a concern. If you have the budget, go for M.2+ HDD else, go to SSD + HDD. You can store those files which you don't really access on your HDD.
It seems for 150 extra bucks you can get the m2 SSD 1TB compared to the SATA3 SSD 1TB price so I may go for it, apparently m.2 is blazing fast.
