I'm an audio engineer, and because of my trade, my hearing and attention to sound detail is probably higher than others. And yes, the PS4 fan bothers me, which is why I prefer to use some sort of headphone solution even though I have a 7.1 system (yes, I can hear the PS4 over it, at times). I, too, do not believe that there are truly "whisper quiet" systems in the wild, as hearing is a really subjective thing. Sony could have done a better job in this regard.
Instead of a "PS4 Slim", I would actually really like a bigger PS4, with a bigger fan. I have the infamous "trashcan" Mac Pro re-design, and even though it has two workstation-grade AMD GPUs and a 6-core processor inside of it, it's the quietest and most pleasant system I've ever worked on, thanks to the design and the cooling solution Apple employed.