Sondigo Inferno 7.1 soundcard
 

It is expensive at $150, and whilst audiophiles will naturally turn their nose up because it's "not a separate", having one of these in your HTPC would make it seriously kick some ***. If you enjoy music or movies and some games at your PC, and if you're the type to spend several hundred anyway on a graphics card/new CPU/motherboard/memory without a second thought, then consider the Inferno to complement it