I don't know how much time and money you want to spend on that laptop, but in general, there are some laptop brands which makes it much more easier to install Linux as others.
I got very good feedbacks with Asus, IBM Thinkpads and some Acer series (as there are special kernel features for these laptops).
Generally, as long as you stay with standard hardware, it should run out of the box with standard Debian kernels. The less standard your hardware is, the more time and configuration you will need to make it work on Linux (at least, that's my experience). That comes from the fact that drivers and kernel support is quickly added for the most popular hardware.
Now, as Alsa is the project currently used to manage sound on Linux (at least for recent hardware), looking at http://www.alsa-project.org/main/index.php/Main_Page
it you soundcard is supported is rather a good idea as well as http://www.linux-laptop.net
to see it someone has already succeeded in installing Debian (or another Linux) on the machine you want to have.
Another general advice is not to buy a top recent material (thereby I mean hardware, not the machine). You have more chances that a driver, even if experimental, has been written if you hardware is at least 6 months old. This isn't always true though ...