I7-6700k running hot package

Did you see that article about "de-lidding" the CPU here?

http://www.tomshardware.com/reviews/kaby-lake-de-lidding-overclocking-test,4970.html

Your high idle temperatures tells me something is amiss with your cooler.
I would expect to see 10-15c. over ambient at idle.

How is your case airflow?
What else is inside?
Is the radiator cooler getting air from inside or outside of the case?

Try taking the case covers off and directing a house fan at the innards.... Does this help?
Any cooler needs fresh air to do its job.

1.4 volt is on the top end of everyday use safe, if you can maintain 80C that is pretty good.

70C at 1.25 is a little high, but normal for non-idle conditions. Cooling isn't magic, the CPU will still heat up, it is where that stability point is that is crucial. Water cooling gives you more overhead to keep pushing the CPU, but don't expect it to run as cool as a GPU for example (They have a lot more surface area for dissipation)

I've found that some BIOS will run the CPU at max clock speed, many have settings to control this.

1. Be aware that the power saving features of your CPU are inactive until the system is "in Windows", so BIOS temps really tell you noting about idle performance.

2. The Asus utility doesn't really measure CPU core temps, it's collects temps from various temp sensors and calculates a weighted average which the BIOS thn uses for carious monitoring and control functions.

3. By 'bult-in water cooling, I assume you are referring to a CLC type cooler. be aware that no 120mm / 240mm CLC has ever matched the performance of a decent air cooler costing less.

4. A Vcore of 1.4 is huge...if not overclocked, it should be 1.2 or less. You might use 1.4 if OC'ing to 4.7 or 4.8.

A. What cooler are you using ?

B. How many case fans are how arranged ? make sure you have 1.5 instakes for each exhaust.

C. You have the radiator fans properly oriented ? They should be blowing in to the case, using cool outside air for cooling.

D. Download / install the following:

http://rog.asus.com/forum/showthread.php?43233-Realbench-v2-Discussion-Thread-Download-Links
http://www.hwinfo.com/download.php

E. Set all BIOS settings to default and go into Windows

F. When you open Real Bench, move both windows to left side of screen. Open HWiNFO64, run "sensors only", you may get a pop up asking whether to disable reading something like the Asus EC chip, click "Disable this sensor". Move the HWiNFO64 window to upper right hand corner of screen. Stretch bottom of window to full screen height. Make the following changes:

-Right Click on "System" right at the top, select hide.
-In the next section, hide the last 4 lines starting "Core CPU Thermal Throttling" (if you watch temps, this is useless)
-Skip over the next section and Hide the section after that (section includes CPU Package thru DRAM Power)
-Now the whole reasons we did that was so you could see everything you wanna see at same time. You should be able to see Vcore 0, 1 and 2 at -the bottom of the window. If not hide a few more lines. Save and Quit will save your edits.[/I]

G. Sit there and watch your core speeds.... for the 1st few minutes, the CPU will generally run at it's default speed ... after a few minutes it will "chill out" and go down to 800 Hz or so ... wait 5 minutes and record, idle temps. Then run the RoG Real bench "Benchmark" (takes about 8 minutes)

Actual RAM Speed - i.e. 1600 (we haven't turned on XMP yet)
Ambient = Room Temperature
Idle Core Temps Before Test on Each Core = i.e. 25, 26, 24, 22
Average Core Temps for Each Core During Test = i.e. 59.6, 58.2, 52.7, 49.4
Max Core Temps During Test on Each Core = i.e. 65, 62, 59, 54
Highest Voltage Reading on any Core During each of the 4 Benchmarks, i.e. Image Ed. 1.200 / Encoding 1.216 / Open CL 1.296 / Multitask 1.248

I notice that your bus is at 133, not the 100 default.
Perhaps try overclocking just using the multiplier.

1. he starting point always has to be at stock speeds as a reference, so you will want those numbers.

2. getting much above 4.5 requires looking at other settings so we want to get that reference points settled 1st

3. If they have incorporated a Helix style reservoir that is of no relevance to what we are discussing.

I still don't know what cooler is in there... Deppcool is buying in from someone, do w eknow who that is ? IS an An Asetec / Coolit derivative, does it have copper or aluminum fan ?

4. The site lists other fans as "optional"... sounds like you have 4 exhaust and 0 intake ? That means the system is sucking in air from outside which isn't likely coming as much from the fan mounts in front as it is thru rear case grilles ... that means all your hot GPU and PSU exhaust is being sucked right back into the case.

5. Using synthetics like OCCT, P95 and such is good if you are interested in getting your name on OC leader boards at various web sites, but is less useful for determining CPU stability and temps that the CPU will experience using real world applications. Asus (JJ) recommends against using them and has done so since Haswell because you can can create scary temps using the AVX versions and testing w/ the older versions without AVX proves only that your CPU is stable as long as no programs are using AVX. Also, you can be P95 / OCCT stable for 24 hours and then fail under RoG Real Bench.

In addition, sythnetics produce extreme heat levels which artificially limit your OC. What's the point of limiting your OC to say 4.5 GHz because it hist 80C w/ P95 and AVX if your CPU will never see that P95 again ? RB contains real programs w/ AVX so when you test w/ it, you know it can handle anything that you could possible run. Also, unlike P95, OCCT, etc, it tests in a multitasking environment. P95 / OCCT doesn't which is why you can be P95 / OCCT stable for 24 hours and then fail in when multitasking.

In any case your idle and max temps/ voltages look just fine, tho I'd still like to see RB results....they should be about 5C lower meaning that you have far less to worry about using real apps.

here's skylake results from overlcocking enthusiasts (162 sample size)

Average OC 4.68
Median OC 4.70
Average Vcore 1.38
Median Vcore 1.38

Here's one of the web sites where folks challenge themselves to get their names high on the charts. There is great info there but try and avoid the mindset whereby throwing stresses at the CPU has some real world benefit. Like if ya wanna know if ya 4WD SUV can get out of the driveway (up a hill) in the snow, you don't need to test it with 6 people , 600 pounds of weights in the back and towing ya 4500 pound boat as you really aren't going to doing that ever .

The two fronts are optional so didn't know if you took that option. Either way, I would go with all intakes except for the rear which forces the air out thru the reare grilles preventing any hot exhaust air from coming in