dude, i think you literally saved me a £700 headache. Luckily my sister is a doc, so i ran to her to borrow a stethoscope and lo and behold, it’s the psu, both sounds seem so close to the ear but it was definitely louder and closer sounding from the psu.Seems strange two cards exhibiting the same thing. I've not experienced anything like that with my Gaming OC and notice no discernible coil whine.
Is the NR200P Max V2 a recent purchase? Could potentially be the PSU as I've seen quite a few reports of the CM850 suffering from quite severe coil whine under load. Could try and create a DIY 'stethoscope' out of some rolled out card or rubber hose to try and pinpoint where the whine is originating. Or try the card in another PC if that's an option.
Darn it, i guess i’ll try to RMA the power supply, but may just buy a new one, any recommendations for a good SFX PSU, 850w+?