> if I will benifit from a 7.1 sound card
No you wont get any benefit from 7.1. If fact pretty much no one will, as very few music sources and movies have 8 channels of audio. Can also say the same for very high samples rates, 24bit audio, gold connectors, etc... as well. All if it pretty much useless for most people.
Having a optical fibre output and 8 separate speakers outputs doesn't make sense if you are using a cheap pair of headphones.
Just use the on board sound card if you have one.
Having said that, there is really no price difference between a 5.1 and 7.1 channel sound card. You can get a reasonable card for $30. Don't pay the $180 for something like the Sound Blaster X-Fi Titanium unless you upgrade the rest of your sound system as well.