i've said this before and i'll say it again - unless you're recording live audio straight in that's being effected by your system during the recording process, or using old or high-end MIDI-based controllers for your music, sound cards are useless. they don't do anything that your in-system chip already doesn't do. they don't reduce your cpu load significantly, they don't offer a significant improvement to your audio unless you're a headphone guy, and they don't really assist in anything that you can't get by just making sure you get a decent motherboard to begin with.
they're just smoke and mirrors, living off their rep from ten years ago (when they were actually needed), kind of like NICs.
unless you want to allow for 5.1 and your internal chip doesn't have the outputs, or are recording midi data or software-effected audio, soundcards are not necessary for a computer.