Thank you for your suggestions.
An ASUS Xonar DGX ,whish has dolby headphone.
It cost even cheaper than a ASUS Xonar U3 at my local electronic store. Should I go for that?
Yeah, I'd go for that...unless you play anything that uses the DirectSound3D or OpenAL APIs, in which case I'd recommend the X-Fi Titanium instead. But both are good sound cards, no question about that.