That'll be pretty quiet i would think (not silent but a lot quieter than a standard PC). After you get a barracuda the main problem will be the PSU. The fan is pretty quiet, but the problem is the turbulence inside the PSU.
But, if you have quiet music or anything else on inthe background, your computer should become almost inaudible i think.
I moved my Q-Tech PSU completely inside the case, and blocked up the hole at the back of the case. And used 2 7V papsts as exhaust. That got fairly warm. So i moved the PSU back to where it should be and put the whole computer in a cupboard
Now literally silent