Sound card for headphones?

I just got Grado SR255 headphones, and I'm looking for a sound card. I thought of getting either CL live 5.1 TerraTec DMX XFire 1024 or Turtle Beach Santa Cruz. Any thoughts about this cards? Maybe some other one that would suit me better, under the similiar price range? I will be
listening to mp3s and playing a few games now and then. I will only use headphones on this card so the surround effects and things like that are unimportant. Also the power of the card isnt important, as I will get a headphone amp. I'm using win2K and Linux, and I have via chipset if that matters anything for the drivers/compatibility issues. Thanks in advance.

When I had the Live 5.1, other people in the room would constantly complain about being able to hear the sound in my headphones (even though it wasn't turned up very loud). I switched to the Hercules Game Theater XP (same chip as the Santa Cruz), and there's a huge difference. Without changing EQ settings, the unwanted sound is nonexistent. I can have it nice and loud, then put the headphones around my neck (4 inches away maybe?), and hardly even hear the sound anymore. Amazing. Sound quality is better, too.

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