..not quite, digital can be compressed in both lossy and lossless forms and so digital is not always bit-perfect.
If you want full surround sound in games movies and music with your system then you will need a card with Dolby Digital Live or DTS-Connect.
Look for a card with 1 or both of these output options. The Xonar DX, may work for you but it is $89. If you have a bit more cash you can buy the Auzentech X-Plosion Cinema for $100, do the Rebate and get the card for $69, which is not bad for that card. It will give you what you want for digital and still have nice analog quality in case you change your system in the future.Good luck on your card hunt.