As mentioned Coil Whine is due to High Wattage Hardware like GPUs, VRMs, PSUs etc.
First you do have a under powered PSU at 400 watts. AMD recommends minimum PSU wattage is 450 watt PSU but other GPU manufacturers recommends a higher wattage PSU then 450. But if the only issue you have is the Coil whine than I wouldn't worry about it unless you start having crashes or BSODs or errors while under heavy loads on the GPU card.
I have read from other Users where AMD Driver have caused Coil Whine in their 6000 series GPU cards. There is not much you can do to fix Coil Whine. The higher the power used by the GPU the higher the coil whine will be.
Input Coil Whine in the Search Box and you will see several 5000 and 6000 series threads concerning the subject.
You can open a Support ticket with the manufacturer of the GPU and see if they believe you need to RMA your GPU card to be tested if the Coil Whine is bad or loud enough.
Or simply install a previous AMD Driver that doesn't cause the issue.