I'm looking for the best possible solution for my system to be as silent as possible.

In my current setup i'm running a 5820k OC'd to 4.2Ghz and MSI 980 ti. Right now i'm looking for a new PSU as my old one is not that great and a new case.
As for the CPU cooler currently i have a Thermalright silver arrow sb-e and while i thought of "upgrading", after reading a lot of cooler reviews i realized it's really not worth it. I'm also not sure if the thermalright fans are ok as i can hear them quite a bit.

Suggestions?

Welcome to SPCR.

Do you have an ATX or mATX mobo? If you want to stay in an ATX sized case, the Fractal Design Define R5 is a great case for big CPU and a single gfx card. If you don't have an optical drive, there's the Define S for a few less bucks and an additional front fan mount.

PSU: Some guesswork on your power load. The i7-5820K has a 140W TDP. If we assume the 5820 truly uses 140W when stressed, then, if you overvolt from 1V to 1.1V to get the 4.3GHz, it raises the load to about 215W. Raising the cpu voltage from 1V to 1.2V means ~256W stress load. GTX 980 TI TDP is 250W. Add another 50W for everything else and you get 556W stress load (if 1.2V CPU). Gaming load will be in the 470W range. For Gold efficiency, something like the be quiet! Straight Power 10 800CM could work. Inaudible at idle/lower loads, fan ramp starts at 250W, and ~900 rpm at high gaming load. For Platinum, the EVGA P2 850W looks good. Fan might not turn on except for heavy game loads.

cpu cooler: Of the two included fans, one (TY-141) has a 900rpm minimum. Could be that, or your fan profile that's causing the noise issues. How are your temps under Prime95 and what's the fan profile?

I have a X99 deluxe. I've heard good things about the fractal r5 and at the moment that's what i'm more inclined to get. I do indeed have an optical drive but haven't used it in years so getting rid of it wouldn't make much of a difference. My only problem with the r5 is that the design doesn't appeal to me that much, but if it's really the best i can get for complete silence i don't mind making that compromise.

As for the PSU i was inclined for the Corsair RM850i after reading this but i will definitively check out the be quiet! psu, especially if it is quieter than the corsair.

As for the cpu cooler, the fans are running at their slowest speed and temps are fine. To be honest i believe the noisiest parts at the moment are the case fans which will be replaced when i get a new case anyway. I was just wondering if the difference from my TY-141 and noctua fans is big or not worth the investment.

Thanks for the suggestions so far. I'm hoping to achieve full silence when browsing the web and getting some work done (mostly programming).

Its not that its not worth it, its a top performer no doubt, specially for higher tdps cpus like yours, but where it doesnt get recommended as much its because its big and specially because its expensive, there are other options that will perform similar for less money, still i wouldn't change it, to me is still one of the best air coolers around.

This you should check, usually TY141/140 were only able to drop around 600rpms and some samples like steve said, around 900rpms, there are also the TY143 (the ones that come on the extreme edition) that i havent tested, but they also only drop around 600rpms or so. My suggestion is run FanXpert since you have an Asus board, and see if you can drop them lower and if the temps you are having are to your liking, if you cant drop them, i would recommend either Thermalright TY-147A (can drop to 300rpms on fanXpert) or Noctua NF-P14r redux-1500 PWM also drops around 300rpms with FanXpert, either of this would be my choice for an 140mm cpu fan cooler. Both fans will fit with your current silver arrow clips.

Once you fix the noisiest part of your build what usually happens is you will start noticing the second. I would say about noctua will perform similarly, the gains for you on upgrading is allowing the fans to drop lower on none loaded operation (like browsing and programming), on load they will be very similar in temps i would think, but all setups are different thus not all can be disregarded, tonally will depend on a lot of things.

Try the included fans first, the Fractal fans should drop around 500 rpms with fanXpert, if this isnt quiet enough for your liking, then consider Antec True Quiet 140 or Noctua NF-P14s redux-900, both fans can drop extremly low, below 300rpms under fanXpert2, some samples very close to 200rpms.

All of the Asus X99 boards have Allow Fan Stop as a BIOS option for chassis fans. This allows a minimum CPU temperature (typically 50C) to be set before the chassis fan will turn on and run. So rather than attempting to set low idle speeds, and maybe changing fans to achieve this any chassis fan can just be set to stay off under idle and low system stress conditions.

Better get rid of it then. You'll free up a few watts, start up noise and time but more importantly get rid of a whole load of clutter.

So yesteday i was messing around with the ai suite and to my surprise it really improved things. Fans are now much quieter and much like Abula said, i started noticing the second noisiest components. After turning fans on and off, these are the parts that emit a noticeable noise, ordered from noisiest to most silent:

- HDD (got 3 of them)
- Case fans
- CPU fans
- Power supply

This was a bit of an eye opener for me because the hdds are being a huge contributor for the noise problem which was being amplified with the fan spin noise. The thing is, i'm using a ssd as my boot drive and the hdds only for storage purposes. But for some reason windows likes to keep the hdds on and i can't find a way to put them on idle (i've already set hdd the power settings for them to go idle after 1 minute). I was running debian recently and never had this problem (well, in fact i even remember having to wait on windows for my storage drive to spin up when i tried accessing it) but some for reason it's not working on my current win 10 install.

Even if i disable all the sata ports in the BIOS the hdd's spin up on POST for some reason.

Suggestions?

Get quieter hdds or better yet, I would get a 4bay nas and place it out of your hearing reach.

Other options you can try is suspending the current hdds or using an enclosure to lower the noise some.

Are they older/smaller capacity drives? You could just buy 1 or 2 newer, larger capacity drives...and if they are just for large storage, go with slower 5400rpm class drives like the WD Green or Red.

As for always spinning up, even with Windows power options set for 1 min sleep, perhaps you have a monitoring utility that's pinging the drives (asking for SMART sensor info) causing them to wake up/stay awake?

Are you mostly hearing read/write head chatter or vibration type noises from the drives spinning?