Need a cooler for CPU

Yeah youll need a better cooler. If you dont plan to overclock, something like the CM 212 evo would do fine.

What motherboard do you have? And how much do you want to spend?

What motherboard do you have? And how much do you want to spend?

That case is a prebuilt cube with a proprietary CPU cooler. From the looks of it, the case panel all but meets the top of the video card. So at best, you have a CPU clearance of a standard height PCIe slot. So I wouldn't bet more than 100mm.

So something like a CoolerMaster 212 Evo cooler at 160mm is completely out of the question.

The system came with options up to a i7-7600 and the cooler is rated to 65w, so you likely won't get proper cooling for the i7-6700k at 91w with the stock cooler.

The motherboard is a H170 chipset, so you're not going to be able to overclock the CPU, if you can even cool it.

In short, I hope you haven't bought the i7 yet. You can upgrade to an i7-6700 and keep all the original equipment but you're going to make life hard for yourself with the K series cpu.

*Edit The Noctua NH-L12 "might" fit and it's rated to 100w. But thats also assuming you can mount it on the motherboard. The system may not be friendly to people trying to get behind the motherboard to mount brackets.

The board looks to be a standard ITX format, so you may be able to pull it apart and pop it in to a new case. If you were to get a new motherboard, assuming your RAM is DDR4, I think you could rebuild it with the existing parts and put it in a new case. But now we're looking at buying a new case and motherboard and CPU and CPU cooler for what started as a simple upgrade to 6th generation hardware. Intel is about to release their 8th generation CPUs, so I'd look at if the cost is really worth it. If it's worth the time and cost to do that to you, then cool go for it.

As for why you can't have the K series CPU in your computer as it now stands, it's a matter of a few things.

1. K series CPU's are unlocked, so you can overclock them. However to do that, you need to have the correct motherboard, which would be a Z170 series board. You have a H170 chipset motherboard. The chipset on the motherboard does not support overclocking the CPU, which is most of the reason why people want a K series CPU. So if you wanted to replace the motherboard, you'd have to find one that fit in your case. Not knowing how proprietary the motherboard is, this could lead to a problems with it fitting and connecting to various ports on the case. Now you could put the i7-6700k in there and assuming it works (see #3) it would run at it's stock speeds. However this leads in to #2.

2. Heat. Your CPU cooler in your computer is only rated to 65watts. The CPU you currently have (i5-6400) is rated at 65watts. So it cools just fine. If you were to upgrade to the i7-6700 (not the K version), it's rated at 65watts and could use your existing cooler and be fine. However, the i7-6700k is rated at 91watts, which means your existing cooler won't do the job. So you have to buy a new one. However because your computer isn't listing it's CPU cooler clearance, we have to guess. As I said before, at a glance, it looks as though you have an upper limit of 100mm, but I can't tell for sure. There's a few low profile coolers that "could" fit, but since this thing is custom made for Lenovo there's no guarantee there isn't something custom for the cooler to fit on to. Judging from the hardware manual (https://download.lenovo.com/consumer/desktop_pub/ic_y710_hmm_20160711.pdf) it looks like there's a mounting system under the motherboard that the cooler screws in to. If that's removable, you could possibly put in a 3rd party cooler. However to get to it, you will have to remove the motherboard, as there is no access hole in the metal under it. Lenovo has a whole series of how to videos for this computer, so you can see how they want you to do things. http://download.lenovo.com/lts/RCDW1250/CourseFiles/player.html

3. BIOS. Your computer ships with the support of a i7-6700, so it's compatible with that i7. However there's no guarantee that the i7-6700k is compatible. While the chipset (H170) "should" support it, it's possible it's using a custom BIOS that doesn't have support for the K series CPUs.

So there's just a lot of "maybes" and "could be" with upgrading that computer to a K series CPU. However if you just put in the i7-6700, it's compatible with all your existing hardware.

Now keep in mind this is just me being bored and looking up stuff on the computer, so I may not be 100% right on this. If you want a definitive and official word on upgrading, then I'd strongly suggest contacting Lenovo customer support and asking them directly.

No to worry, it helps pass the time when I'm bored at work.

So short answer is no, I wouldn't recommend buying a new case, motherboard, cpu and cooler for your current hardware.

If you're looking to do a new build or buy a new computer, I would wait until Intel releases their new CPU. The costs aren't going to be a huge difference and the performance will be better. Since you'd have to buy a new motherboard and cpu and cooler anyway, you might as well do it with the latest model instead of spending only a little less to build with the older models.

If you just want to upgrade the CPU and keep everything the way it is, then go for the i7-6700. It's cheaper and easier to do. Honestly this is the suggestion I'd recommend. If it provides enough power to do the things you want to do, then great. If not, then sell it and build/buy a new one once the new Intel stuff comes out.

One thing I will also mention. Your motherboard might support the i7-7700. It uses the same socket, so it might just need a BIOS update. It's a little faster of a CPU than the i7-6700, can use the same heatsink that you currently have, and is only a few dollars more. Contact Lenovo and see if the computer can use it.