Hello. First off I will start by saying that I have the Sennheiser game ones for gaming with an external Creative SoundblasterX G5 AMP. I have tried on board audio with these headphones and it just doesn't put out enough volume for them even at max. The problem I am having with these headphones and the Amp is positional audio. I don't use 7.1 channel or any surround sound as I have tried and it sounds even worse. When I hear foot steps or gun shots in game I basically have to look around until it's centered for me to know where it is coming from. Is there anything I can buy externally that is better for positional sound than this Amp? Thoughts about the Sennheiser GSX 1000 AMP?
Unfortunately, positioning on stereo headphones is never going to be perfect. You might want to consider getting headphones that actually allow surround settings. They will not sound as great for music but should help for games.
If by centered you mean height on the screen there's the limitation of not having actual, physical Dolby Atmos speakers, since height is hard enough to replicate on a normal surround speaker system let alone 2ch headphones simulating surround sound. I use positional audio too but I don't expect it to be so precise as to allow me to shoot through walls just by sound and actually hit somebody (not that there are even games with the right physics for me to maniacally unload a rail gun that way and actually kill somebody like in that Schwarzenegger movie where the rail gun has thermal imaging sights). Actual Atmos speakers and better audio encoding on games. Oh and only when Atmos includes floor speakers. Until then...well...don't expect to be able to shoot through walls based on audible footsteps. Also if your games already have surround headphone audio in the options somewhere you don't really need a soundcard that won't do that much better either. Most commpetitive games have this built in.