your best bet is to take a look at the hardware that your Linux distro supports. I'm sure there's a file on the CD or on the website that will let you know what will work and what may work. You may be able to check the websites for the soundcard manufacturer to find out if they support Linux, or Linux sites post info on third party driver development.
Check out the <A HREF="http://www.alsa-project.org/alsa-doc/" target="_new">ALSA project</A> for a list of sound cards supported under many of the Linux distros that use ASLA sound card support (SUSE and Red Hat are two). It does look like the TerraTec cards are supported, so that may be a good choice. Also some of the Hercules and Turtle Beach cards, along with Cirrus chips used on Mobos, are supported as well. With the requirements that you gave, you should be able to pick a card for under $100 if you wanted.
Jarrett
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