for a little bit of future-proofing, you won't get wrong in choosing either the H170 or even better the Z170. The later comes with additional support of 20 PCIe lanes by the Z170 chipset, exclusive of the 16 direct PCIe lanes provided by your i7 6700K (a total of 36 PCIe lanes), in which you can play around later on in expanding your system for your IO peripherals, for example, a NVME SSD, a PCIe-based storage, a faster wifi card, etc. This is important in case you want to do SLI in the future, who knows right? Furthermore, you choose to go for the K version of the i7, so Z170 would be a better choice there.

and to answer your question, 650W is good enough for the above specs, but you never know if lets say in the near future, you wanna add on another one card and maybe do some OC on your CPU and GPU, if I were you, I'd go for the 850W, just for the future upgrade and better efficiency of the PSU operating at half the rated wattage, generally. I did this mistake by buying the 750W, coz I have the plan to do some SLI also later in the future. Wasting a lot of money by buying low wattage then gatal wanna do SLI and need to buy another one. Poor initial planning really.

make sure you're using the correct version of the HDMI cable. To be safe, use the v1.4 version as that's what the HDMI input of the X34A supports (refresh rates locked at 60Hz via HDMI). Otherwise just use the included DP cable, since your GPU also has the DP input, which in turn supports the 100Hz refresh rates.

the future should be ultrawide with HDR now instead of increasing the refresh rates to absurdly 200+ Hz.

true, no need give yourself a headache being surprise over the size of a 4K mkv. Just get a good 21:9 RIP of ANY video files, it's good to go with the X34.

Anyway for better rendering of those vid files, try have a look at madVR filter. It's that good!

Nvidia has been a sucker for propriety tech. Now buying monitor alone has to be divided based on what GPU you use. They dont want to conform to widely-acceptable, open standard making things hard for end users. They wanna have some pieces of the pie out of monitor sales also. Greedy as f**k I'd say. But not all of the blames are on them. They are a business entity. Their cards have been best sellers for the past few years due to Radeon incapability to release cards that could compete with them. I wish Vega would change things up like what is happening now with Ryzen.

Those who have been waiting for the X34P can just proceed to buy this one, Acer Z35P 120Hz of goodness!

http://www.guru3d.com/news-story/acer-z35p...and-g-sync.html

OMG it's happening!

http://wccftech.com/asus-announces-rog-swi...te-hdr-support/

Curved? Check. Quantum Dot? Check. HDR? Check. 200Hz Refresh Rate? Check. ULTRAWIDE? Check!!

now let's guess how much will this be?

That's for sure.

I'll take the cheaper one if it differs by a huge margin. Same panel is what matters however still have to wait for the final RRP. Can foresee some people will try to offload their X34A in Garage Sales then.