When I look at the X-Fi's spec sheet, I'm not impressed. I admit I've never heard it, but based upon it's specs, I see better in the 8788 or Envy24HT. I realize potential capabilities of any particular chip can vary greatly when you consider the rest of the components on the PCB, but to say an X-Fi is going to give better audio performance over a good receiver with quality components like burr-brown/TI or AD or even Wolfson DACs is simply Creative Labs fanboyism.
I don't want this to turn into another X-Fi vs. The World thread, God knows there's plenty of them. To the OP, look around, there's lots of options out there, many that actually work with Vista. Creative is no longer the only company producing excellent soundcards for PCs. Someone posted yesterday about a new card from Audiotrak that looks very tasty.