STX is a great sound card. Because of the power and clarity of it's amp section it will open up your music quite a bit. Also, it has built in Dolby Headphone processing so you will gain a huge plus in your 5.1 headphone emulation. The STX is a great card and I have zero complaints about it when combined with my Stax 404LE's and my Senn 595's
And man, it does sound awesome for 99% of my tracks, not only through headphones but even in my car.