So i've decided that quietness is most important to me when it comes to my main rig and I want to get it as quiet as it can.
I have the Fractal Design R4 windowed version (although I am wanting to get the regular non windowed one, or try find a regular side panel for sale, idm if it's second hand, I might make a thread about it). It has 2 Fractal design silent fans that are on the built in fan controller and are inaudible over the slight hum of the HDDs when on the middle setting of 7.5v.
I am going to be getting either the STRIX edition of the asus 980Ti or EVGA's top model depending in how loud EVGA's is because I've heard that they're like vacuum cleaners :/
How ever, my possibly faulty CPU is always overheating and needs a pretty decent cooler for stock clocks, so I was thinking about getting the old noctua blah blah-14 model because it's quieter. However, I won't be overclocking, or not much at least, I just won't an OP cooler that's silent, and near silent under gaming load.
You could go crazy. Get a PCI riser and mover the GPU away from the board a little. Remove the cooler and get a suitably large CPU cooler, mount this to the GPU and have fully passive or at minimum super quiet slow noctuas.
Sound like you have what you want in mind but the ultimate quiret would be a large wooden box with the motherboard in the centre, good 4 inch clearance on all sides and 2 inch foam to deaden the sound. That leaves 2 inches all round for air flow, cabling and what ever else you want.
Off the wall but damn I would love to do it just to have a completely silent PC.
Also, a truly silent PC is one that isn't there, or is at least as far away as feasibly possible. (that means get it off of the desk) Unless you get rid of the hard drives, go with a GPU & PSU with a no fan mode or passive, do not use any AIO water cooling, and run your fans on the lowest setting, you will be able to hear it.