Which should I upgrade to get best sound, mainly for gaming and MP3 playback. My speakers, I thought of getting the Logitech Z-5300 to replace CambridgeSoundworks FPS2000 Digital (that I'm forced to use in analog mode anyway) or should I replace my soundcard, which currently is an SB Live! 5.1 with Audigy2 ZS? I also use headphones heavily (quality Sennheiser HD600). Which of these two upgrade options would provide the best improvement in sound quality and overall gaming experience?