I7 6700k build ( need help with cooler and PSU )

You should be able to overclock to 4.2 GHz as 1 of my friend has had the same cooler on his 6600k and his max temp was 70C. Also I recommend you change the case as the cooler will probably won't fit.

http://pcpartpicker.com/p/rFxLvK
Same build only case $3 cheaper and fits cooler fine. Case looks nice as it's the snow edition.

I myself went with the NH-U14S, really like it, noise wise you might want to go 140mm too, but for cooling that 120mm one keeps it cool enough too. You might want to look into another PSU, SeaSonic is really good, but for the same price or slightly higher price you could get a 650W fully modular 80+ Gold PSU.

You might want to get a bigger case, but that cooler should fit, it's tight though, that doesn't impede how well the cooler works, but it might be really frustrating to install and work on your system, although you don't do that every day.

As far as overclocking, it varies, you can have bad luck with a chip and need stupid voltages for even 4.4GHz. Mine does 4.4 on stock voltages, I got lucky.

With an average chip, that cooler should do more than fine. And for fun, check the auto voltage your mobo gives the 6700K. A lot of mobos overvolt the shit out of it (mine gave it 1.350V on stock clocks, which is wayyy overkill). Stock should be about 1.200V.

First of all, Define S, I've got that one, it's amazing. I didn't want bays for CD/DVD/BluRay players, since I don't use them, a simple design, good airflow, and silence. It's got all of that. Really recommend it!

Overclocking can be quite daunting, especially the rebooting, stressing, failing, trying again. It will cost you some time, I think it's quite fun for a while, but I didn't want to really push it to the max either (for the same reasons as you: not necessary, and more silent).

As advice: you are right. Because if you set a manual voltage and overclock (no speedstepping / c-states) it will run at max voltage and overclock all the time. You want adaptive + offset (< BIOS option for CPU voltage, can be called something slightly different, but most 170 boards I've seen call it exactly that).

Your actual voltage (at load) will be your adaptive voltage plus the offset voltage. The reason for this is that all the different voltages the CPU uses (running at different speeds, so different voltages) will also need to increase for stability. Because it calculates different states based on the max speed, if it would run 4.0 max, and the step below that is 3.5, it will now become something like 4.4 -> 3.8. That 3.8 state will also now need more voltage than it did before the overclock.

Here's the kicker: it also calculates the adaptive voltage in the same way. But, since the higher your overclock, the more voltage it needs (it's not linear at all, a 200MHz jump from 4.0 to 4.2 will need a way smaller voltage increase than 4.4 to 4.6). So if you would just use adaptive, the voltage for all the states below the highest one will get way more voltage than they need. This is not dangerous, but ineffecient. So it's better to have the states as close to stock voltage with an offset, than just a division of the max adaptive voltage.

It's a bit complex, but it's more playing with the settings than anything else.

Before you even start overclocking, make sure you read up on everything. There are some really weird differences between information. Different people liking different things, plus actual wrong information on tech spec sites. Intel lists the max temp at 64C. That's not even close to the maximum temp. I don't know what they mean with that. Maybe something like over 64 will start to shorten lifespan? Idk. A lot of people say stay below 80 at load in a stresstest (that will be 70 to 75C on actual load, stresstest stress the CPU more than a program, even if that program uses 100% of the CPU). But since I went with a small overclock like you are planning, I wanted to stay way below that. Turns out my CPU never gets hotter than 63/65C. Which is awesome, that means it will never get that hot in actual usage (the max temp was using LinX).

Good luck on your journey! Don't forget to mark a solution, and don't hesitate to ask further questions!