If gaming is your primary choice you should not pick up the Essence STX or the Titanium HD as these were designed specifically for music lovers in mind. If gaming is your main focus as you stated above and you are looking for decent music quality as a secondary option you should get a card more catered towards gaming (gaming cards and music cards have different sound signatures). I know Creative just came out with the ZxR and they have their Fata1ity series gaming cards as well as Asus has the Phoebus card.
I would upgrade in steps. First step would be to get a new sound card or amp/dac and keep the headphones you have.
Try them out for a couple of weeks then make the decision on whether or not to buy new headphones.
A sound card or amp/dac do make a big difference to what you are hearing.
Edited by velvetx - 2/5/13 at 11:41am