@Kalanen:
I own a somewhat "silent pc", HD600s and x-can v2, tried Corda HA1 before.
IMHO making your PC less noisy is a very good idea. But it might be hard if you did not chose components especially after the noise they make (harddrive, graphics adapter, mainboard fan?).
I do not notice my PC at all when listening to music, even at low volume levels. (I listen at pretty low levels most of the time.)
Regarding HD600 and Corda HA1: Test it with your setup before buying it. I found the sound to be pretty cold and "without emotion", especially at lower volume levels. Very detailed, but also very boring.
The bad thing about the HD600s is probably the amp thing. The phones did not sound that bad connected directly to my soundcard. But after listening to it on a integrated NAD amp, I thought I needed an amp to get more powerful sound.
The x-can v2 amp was nice for a time but is very far from perfect. I'd love to get a *really* good amp for the HD600 - which would make things pretty expensive.
Plus, my sound source (envy24 based exw24/96) turns out to be maybe not as good/excellent as I thought it is (in the upper frequencies). But I am not sure about that.
Herbie