Unfortunately, the answers you received were only half right. I too own the Sennheiser Game Ones, and they REQUIRE an amplifier to be effective at all. Onboard motherboard amp / dac is garbage, and the sound quality itself will suffer unless you purchase an amp that can drive these headphones the way they were made to. I will tell you for sure if you bought these and are just connecting them up to your motherboard, you are in for a huge surprise when you finally get an amp. The GSX 1000 is supposed to be pretty good when paired up with the Game Ones, I personally use the Astro Mixamp Pro TR and it works great with mine, and its night and day difference to my onboard sound card. The resistance of these headphones is much higher than your standard cheap gaming headphones, which is why the amp is required for these to really do well.
As for the positional audio and actually producing the virtual 7.1, I dont have first hand experience of the GSX to provide you with a clear answer on it, but what youtube video reviews are saying is that its decent to good for this as well.