i would just get a 8800GTS 320MB and a 30$ creative sound card, you dont need to spend THAT much on a sound card, but if you really do than you the Fat1lty X-Fi
My x-fi sounds awesome on music, when it works, the drivers are as buggy as hell, creative dont give a toss even though i spent a fortune on it. Im an audophile a geek if u will when it comes to music so i can really tell the difference, i had a creative live 5.1 before this and i can def tell the difference.
you should be able to hear the differnce. Especially on games, movies etc.
But of course speakers have a huge effect too.
But overall I don't see the point in spending a lot of money on a sound card, unless you really need it (some professional stuff) or you have way too much money on your hands.