Well, I decided I'm going to turn the PC I bought into a DAW (digital audio workstation) for my studio (I did build it for that purpose). Problem was the CPU was much too loud to be able to do recording with. So I dropped by one of the PC stores in the area and bought an Arctic Super Silent Ultra TC heatsink/fan. I was really worried that it would be a waste of money (after trying other fans in the past). This setup is awesome. You can't hear the fan running at all. Now the loudest part of my system is the hard drive when it spins. Damn Seagate. I've also got an Antec Sonata case and the case fan and PSU fan are incredibly quiet. It honestly doesn't even sound like it's on. Simply amazing. So now I just have to decide on a new soundcard (I'm thinking an RME) and an external mixer (Allen & Heath). My PC is even running like 15C cooler.
So if you're looking for an ultra quiet PC, the sonata case with the arctic fan is hard to beat.
Can anyone recommend a quiet SATA hard drive (80G or >)?