I realize this is a really old thread, but where did you find the output impedance of the ALC892? I have the exact same motherboard, and I've been looking all over for this info. I recently got a pair of Sennheiser IE80's (16Ω) and I thought it was odd that the sound card my brother bought for me causes them to clip slightly during certain songs. It's a Sound Blaster ZXR, and I don't have the 600Ω amp switched on, which would probably damage the earphones. Digging up what I can on the sound card, I've only found from other forums that this has around 10Ω output impedance... awful for in-ear's. If you're right about the Realtek chip, then what is the point of a $200+ external card that doesn't work with normal headphones... I feel bad for not using it except for the optical to my receiver.