I need someone to hold me tight & whisper in my ear that it's all gonna be OK

Sup folks, as like...3 people here who know me know, I recently had the opportunity to bring my rig up to snuff - 2500 for a 2700K, OC'ed to 4.6, dual 670s dumped for a 1060, various case pieces to replace damaged bits (it's a Lian-Li, there was no simply replacing the case. Yes I'm a fanboy leave me be), and the biggest spherical genital ache, the cooling mods.

My NH-D14 only had 1 fan on it because on literally the first day I got it I broke one of the fans by picking it up wrong. But a 2500 never needed anything more. An OC'ed 2700K on the other hand...so I replaced the 2 140mm intake fans with P14s, added a P12 to the CPU cooler, and replaced the exhaust with a P12 too. Set it all up to run at around 700rpm until it gets toasty, and let the baby fly...and fly it bloody does.

The temp right now is 46c. That's with 800RPM on the 140s, and the 3 fans near the cooler. WHY?!

During gaming it's not too bad it doesn't go above 55c. But surely my ambient temps should be lower ? Have I screwed up my OC ? It seems to underclock just fine (runs at 1.6ghz most the time).

I'm out of my element here, I'm used to just banging in a whopping big cooler and letting it run, but being an old fart my tinnitus means I have to keep a check on the noise.

If you are targeting a quiet PC, with the large cooler and speed dropped 140mm fans, less than 55 at a push is a good for an OC system IMO. What is the ambient room temp?

The anomaly is the 46 idle. I don't know if anyone else knows but 1.6GHz idle seems a little high. In my experience they idle below 1GHz. I don't do much overclocking but perhaps it is worth reviewing your CPU settings or checking what is running and making sure nothing is keeping it spooled. If there's no joy, the temps seem perfectly fine for the long haul even if it might mean a hit on your energy bill. :P

A) what thermal paste and is it worth reapplying? I would seriously look at that.
B) air flow.... case airflow all going the same route is important...look at it with a critical eye and make sure you're allowing air to move THROUGH and not all pulling or pushing

And you say it's underclocking fine, but it is also undervolting fine on idle?

There can be other odd causes - heat from a passively cooled 1060 for example (if it's a model where the fans spin down).

The temperatures are fine - you are worrying too much. I have a Xeon E3 1230 V2 running at stock clockspeeds with a Corsair H40 water cooler and it can hit around 70C.

Edit!!

Remember you have overclocked and overvolted the CPU too. Also were your GTX670 cards ones with blower coolers??

Ambient case temperatures are always going to be higher than room temperature. Once your computer has been running a bit the heat will have soaked into all the components and the case. And this heat will radiate out.

If your components aren't getting too toasty, I wouldn't lose any sleep over it.

You can improve efficiency by ensuring there are no obstacles in the way of the air-flow (big grills, swish looking front panels). Air doesn't like changing direction and will also follow the path of least resistance.

But ultimately, moving air is noisy.

You could switch to all-in-one water cooling that reduces some of the noise (but partly replaced by pump noise).