Since you're running Linux, you can simplify your life and just get another Squeezebox. That way you can use the same Squeezecenter server software and it makes it pretty slick for having multiple SB's. (I use 2 of them, personally.) I think you'll find this a much simpler solution that setting up a soundcard, finding client software for Linux that you like using, and pointing it to the same location as the source files for the Squeezecenter.
Just my 2 cents.
Michael
Just my 2 cents.
Michael