Didn't read through all of the posts/thread - but - I second the person (and others also if mentioned again) getting at least an ASUS Xonar DG.
I recently got my Xonar DG and needless to say I'm impressed what big sound is packaged into such a small card with a small price. It's not a great card for surround sound or 5.1 as it lacks DD Live! and other licenses, but for headphones it's fantastic.
If you're into the headphones and you also like to swap to good 5.1 (for gaming or otherwise) I suggest getting the DX/D1 as they have all the DD goodies.
And I'd really love to get the razer mamba.....