The Asus Essence STX is a superb card, agreed it doesn't have 5.1 support, the sound through even moderate speakers take some beating ( don't be put off by posts reporting driver problems , mine works fine with latest Asus ones ). Many people on this forum use Sennheiser PC 350 headset as a combo for gaming, everything depends on your budget. I intend to buy the PC 350 SE after sampling them with both games & music, truly amazing quality.
If you can afford it the new Sennheiser PC 363D provide a solution for what you are looking for, it includes an inline USB sound processor for 7.1 but at a price !