[Qwerti]

Would there be any noticeable degradation of sound if I upgraded from onboard ALC892 to a Xonar DG soundcard with an output impedance of 10ohms. I have read that you want the output impedance to be 1/8 of the headphones.
I really like the sound of my Note 2 with lots of bass boost with the DSP Manager on Cyanogenmod.
Headphones I have is the Ultrasone Pro 900 with an impedance of 40ohms

 

[PurpleAngel]

  Would there be any noticeable degradation of sound if I upgraded from on-board ALC892 to a Xonar DG sound card with an output impedance of 10-Ohms. I have read that you want the output impedance to be 1/8 of the headphones.
I really like the sound of my Note 2 with lots of bass boost with the DSP Manager on Cyanogenmod.
Headphones I have is the Ultrasone Pro 900 with an impedance of 40ohms

Chances are the Xonar DG will at least sound a little better then the ALC892.
The DG should have a lower headphone output impedance then the motherboard.
Also the DG comes with a basic headphone amplifier, which I'm sure your motherboard does not have.
The DG's CS4245 DAC chip should be better then what the motherboard's on-board audio provides.
The Xonar DG is $26 and there is a $10 mail in rebate this month (Amazon).