i need help picking a cooler for an i7 8700k

Sounds pretty good to me.

Depending on what version of Prime95, anything after version 26.6 will use AVX instructions. This has a net affect of running the cpu closer to 120% as far as relative temps go on Haswell or newer cpus. Ivy-Bridge and prior don't have that technology, so AVX doesn't affect them. Version 26.6 and prior also doesn't use AVX, small fft is realistically the same as a 100% gaming load as games really don't use AVX either.

So when using new versions of stuff like Cinebench, RealBench, p95 etc temps can be a little nuts due to AVX.

There's a couple ways around this, you can set bios with an AVX offset, -2 will drop the cpu 200MHz whenever the cpu uses AVX, which will keep temps more regulated or simply use p95 26.6 small fft.

Keeping temps down while gaming might be accomplished by adjustment of fan curves, the cpu could care less exactly what the temp is, until it's at throttle/shutdown temps, so for it, 65°C is exactly no different to 45°C. So default bios fan curves are set to keep the cpu cool at under @70°, and thats all it intends to do. If you personally want 50-55° temps vrs 60-65° temps, bump up the fan curves of all the fans, intakes, exhaust and cpu. Better airflow means better possibility of more effective cooling.

Optimal airflow on a mid-tower is usually 1x 200mm, 2x 140mm or 3x 120mm intake with roughly the same exhausts. Depending on your perspective and just how much you buy into the positive or negative pressure theorys, with 3x 120mm is slightly higher possible cfm than 2x 140mm etc, but that can easily be changed with fan speeds. So 2x 140mm could put out @ 160cfm at 1000rpm whereas 3x 120mm at 500rpm and you are looking at just 60cfm etc. So finding the right balance of air in vrs air out is actually more important than just throwing in fans.

Placement counts. I've seen ppl put 4x intakes, including a 120mm in top rear, and just 1x 120mm exhaust and can prove that cpu temps are lower as a result. But that doesn't include the fact that that top fan is blowing any gpu heat back on itself, and you are opposing intakes, so case temps are far higher than they should be. Airflow is exactly that, air flowing. It needs to go in and then out, not spin circles around inside the case.

Exactly how much you'll need or want or insist on is up to you.

With a tower cooler the only fan thats really necessary is the rear exhaust, that's a must for cpu temps and removal of heatsink waste as that's exactly direct from the cpu fan exhaust. The rest is somewhat optional as long as the air flows in/out.

With an aio, p95 tests take a minimum of half an hour, it takes that long for the liquid to stabilize at its max temp. Many tests with fan curves are similar. A quicky test with curves will not change results much, the tests will by necessity require extended periods at temp, just to see what if any the results are. The cpu and gpu temps and case temps and drive temps all play a different role, bumping the curve up slightly may not seem to have changed anything, but you could just have changed internal pressures and gone from a dust shield to a dust magnet, something you cant/won't see for a month. Or it might just be enough to drop drive temps 2-5°C during extended gaming, which can be important to ppl using m.2 drives as they are notorious for running hot.

Wuth fan curve adjustments and/or fan additions there are no quick and easy answers usually unless your airflow is that bad to begin with.

malik11,

Since you're measuring 78 to 80°C in your present case during P95 v26.6 Small FFT's, if that's at typical daytime summer ambient temperatures, then I wouldn't replace your D14, but a case upgrade is fine.

Here's the operating range for Core temperature:

Core temperatures above 85°C are not recommended.

CT

You are going to get better results delidding than you will replacing that noctua. I seriously doubt you will see much of a change between that noctua and 240mm aio. Guaranteed the horrible Intel paste is bottlenecking your thermals right now.