First I would recommend you to check that amarok is really "killed".
Do this by running (in a terminal):
ps -A | grep amarok
If its still running, you will see a line like this
4184 pts/1 00:00:02 amarok
The first four or five digit number is the PID of amarok (in this case PID=4184). You can use that to kill amarok, this way:
Now, if sound is still dead, you should try to restart your sound system. Here you can find info about how to do that: