I really feel your pain, this very thing is what made me decide to move in my current complex. It is as quiet as if I were in a house, very well built buildings. It is also the most expensive place I've lived so I am considering moving this year (sadly) but it is what it is. For me it was the all of the stomping around, creaking floors, party sounds, major arguments, etc. that kept going on both over-head and next door.

I hope you are able to find a viable solution!