Got my Mac mini replacement today, and it has coil whine too...
i dunno what to do, replace it one more time ? try a different build ? go for a Hackintosh ?
Would the size of the SSD make a difference? I went big and got the 1TB and don't hear a sound. I work usually at night when everyone is asleep, and I record music, so the house is quiet and the Mini is virtually silent. It has been - for all intents and purposes, dead silent. If I put my ear, literally to the machine, when the house is dead silent, I can barely hear what sounds like a mouse in the distance, playing cards. Tiny little scratching, intermittent sounds - as soon as I move 6 inches away, silence.
I have the i7, and I have tried to push this machine to get it to get hot and to get the fan spinning, and it has been so stable, and quiet and hasn't gotten hot either. So far I am really happy with it and actually glad I didn't go the iMac route this time around.