I use Realtek ALC1150 onboard on the ASRock Extreme6 board with onboard amps and digiZoid ZO2.1. I have a SoundBlaster ZxR sitting on the shelf too as I prefer the sound of the onboard which is by far the best onboard soundcard I've ever used but I will probably have to give ZxR a try with Yamaha as it could have better synergy and the ZxR is pretty warm sounding which is exactly what I'd need, a more warm/smooth sounding source to get closer to my preferred sound. I have to set the bass boost a few levels higher to get to that preferred level compared to Q40.
The main prob as it is now, seems to be the highs, they are a bit too shrill which creates a slightly cold signature that doesn't make me get into the music, I'd want a tiny bit more warmth, think Tube amps and the sound would be far better. Vocals and hi-hats etc doesn't have that much raspiness to them in real-life as I'm currently getting with the Yamaha, it's more the character than quantity of the highs that is the issue.
EDIT: Doesn't look like the result out of ZxR is any better, if using the amped headphone out the mids slightly improve (the only real thing I truly enjoy out of the ZxR in comparison to the onboard).
Do you have good return options?