will a sound card make any diff over on board sound

[cyrus883]

hi all my system is a thermaltake dh202 xp pro 64bit dual core pc using cyberlink power cinema as my media player using spdif out into my cyrus avmaster8 to x2 cyrus 8 power amps with x2 cyrus psxr power supplies my question is if i go and spend good money on a sound card will it make a difference over the on board sound realtek ac97, i use my pc for tv dvd and music and i also use the pc as a recorder in analouge off my rega armed technics 1210 turntables any advice on this would be great also if anyone knows of a good sound card to use please let me know thanks all steve HAPPY NEW YEAR