Compuser10165 :
I agree with you. I just was pointing out that the 850w was worth the difference (it's not like 50$ more). Also, numerous benchmarks show that Skylake architecture has a greater benefit from faster RAM than other platforms (both DDR3 and DDR4 platforms), so that is why faster ram is more recommended in this case.
First, never recommend high speed DDR3 on a Skylake build. I know you didn't here, but you mentioned it so I wanted to make sure you know not to. Using anything with a voltage above 1.35 V can cause damage to the IMC, which is why Intel only officially supports DDR3L. DDR3L mostly tops out around 1600-1866 MHz. Similarly, it is better to use DDR4 using 1.2 V, as that is the official recommended spec. Which, again, you suggested a good RAM kit, just sharing a little info on the IMC.
As for the PSU, if the user plans to use more power later, then that is a better option to get the 850 W unit. If not, the 650 W unit is better from an efficiency standpoint. PSUs are most efficient around 80% load. They are typically list efficient under full load, and kinda in between below 80% load. It is best to consider about how much power a user needs, and pick something that offers 20% more power. That way the amount of heat and power consumption of the system is minimized as much as possible. To get the most efficiency out of a 650 W PSU for example, you would want a system that pulls about 520 W of power, which is fairly close to the power estimates for this system.
An 850 W PSU is best reserved for if he is going to for sure use a multi-GPU setup or run numerous storage drives, as those add up about 10 W per drive. For example, one of these setups, plus a half dozen HDDs and a 750 W PSU would be the optimal solution, but if a well priced one isn't available then the 850 W PSU would be better, as it is best to remain under 80% load than exceeding it.