I also use gaim and have the sounds turned on within its preferences. In the Suse control center, there is a sound and mutimedia option, that has a sound notification option. Under event source are listed all the applications that are configured for sound. Gaim is not among them, and there doesn't seem to be any option to add it, which is why I thought it might be possible to do so using the command line.
I am not sure there is any command line options like that for gaim. I don't know why you want the sound stuff in Suse Control Center unless you want to control all at one place, but I think I would be too much and not worth it to do that. What is the sound notification option for anyways?
Thanks,
Jonathan