If you are using KDE, you should try making arts' the sound buffer smaller or completly desactivating arts (any way, arts is a software sound mixer, but with a card like that, you have plenty hardware mixed voices). To make the sound buffer smaller or to turn off arts, go in your K menu->Settings->Sound & Multimedia->Sound System. You will have a slider for the length of the sound buffer and a check box "Enable sound system". This check box will not make your computer silent, it will just disable arts and you will use the hardware sound mixer on your card instead (wish I personnaly recommand).
If you choose to disable arts and you are using system notification sounds in KDE, you will have to go in your K menu->Settings->Sound & Multimedia->System Notifications and then click on the "Player settings" button. Choose "Use an external player" and type the command name of your favorite sound player. "playsound" should work fine. If you play music trough amaroK, make sure your sound engine is not arts, or you either won't hear your music, have an error message or arts will start automatically when you play music.