Question about Debian

[Christian]

Hi all,
First, I know that this has been up before but I need to get help on this.
I have two sound cards on my system, one integrated on the mainboard, A Realtek card which I am not able to disable at the moment and a Soundblaser Audigy 2 ZS which I want to use instead. How do I change that so that it is the default in the entire system?
Also, I have downloaded the testing version. If I look in /etc/apt/sources.list i see squeeze. If I want to try the absolute latest packages, like Gnome 2.27 should I change to sid, is this correct?
Many thanks for any info,
Christian