ext sound cards- any recommendations ?

[mec2]

recently bought a dell optiplex 745. while i like the computer, the sound card really sucks. unlike a tower, this is a very compact unit and due to physical limitations i'm pretty much stuck with the card that came with it. any "serious" recording will be done on another computer with a prof sound card in it so i only need the new card to be clean, quiet and play cd's, mp3's and streaming audio with decent fidelity and clarity [a respectable S/N ratio would be nice also].
a search turned up 3 possible cards: Sewell USB SoundBox 7.1 USB Sound Card,
StarTech.com External USB 16BIT 7.1CH To Audio Adapter Sound Card, and a
Sabrent USB-SND8 8-Channel USB 2.0 External 7.1 Sound Box.
i don't know "jack" about any of these. anyone had experience with any of these ? maybe you know of a good ext card that's not one of these listed. any recommendations ??

thanx