I thought I'd not notice going to onboard tbh, but it was noticeably terrible, at least in games. Gunshots etc just sounded dull and I couldnt hear all the little details I normally could. I have an Asus P8Z77-V Pro board. When I tested the onboard sound it wasnt overclocked since I pulled the sound card while chasing instability in my system (i thought it might be the sound card causing it).
You seem to be a little deeper into the audiophile thing than me so you probably have more experience with that grade of equipment. For me, the living room has all the big sound goodies, the computer is more for work and gaming, neither of which needs anything more than a good gaming card and set of cans/speakers.
