If you want to go
hardcore, you might want to look at external USB/Firewire-soundcards.

Yes, I hear very good things about the developments in Linux compatibility of Firewire based cards. This page might be worth some atention;
http://freebob.sourceforge.net/index.php/Main_Page

You might also be interested in this page on Alsa compatibility;
http://www.alsa-project.org/alsa-doc/

In general I think that provided finances and space in laptop-bags can accomodate one nobody will regret going from a buil-in card to a pro or "prosumer" card. Latency aside there is a lot of difference in sound quality.

Kas.