Take a look at the Fractal Design R4. I used the Arc Midi and now the have a ver 2 out but I think the R4 has isolating foam installed to make it super quiet. It is slightly above the $100 mark but it looks worth it.
It has a physical fan controller so you can make it very silent, whenever you got clients. If you want to do something intensive like gaming, rendering, editing and your hardware becomes hot, then you can easily just ramp up the fan speed by a simple push of a button on the front and get better cooling.
It also has sound dampening material in the front and on both sides.
It has space at the top for a dual fan radiator and a detachable harddrive cage, if you need space for a REALLY long GPU, so no problems with the space. It also has quite large space for your cable management behind the MOBO.
If you wanna look proffesional but still be functional, then the R4 is the way to go.