I managed to get ALSA to work (without any fuss actually) and I can now play sound using XMMS. But the problem is that KDE refuses to start sound (giving the usual error message about no device found) at startup.

I went to KDE Control Center -> Sound and Multimedia -> Sound System and tried different settings there, but none works.

Sound in KDE works in Gentoo (ALSA) and also in Debian (OSS).

This is probably a newbie question, but how can I make sound work in KDE? This shouldn't have even been a problem, but I don't know. Maybe a permissions problem?

Yep it's likely a permissions problem. make sure your normal user is included in the audio group.

Yes. The normal user is in the audio group.

Also, I noticed that even when logged in as root, the sound doesn't initialize in KDE