I've had z680s for a year, sound is great for mp3s/games.
edit: The only thing is if you're using/going to use a creative soundcard and want to use digital connections then you're fucked, creative still haven't got dd encoding i.e. ac3, they use their own bastardised version which has 3 outputs instead of just the 1 so the only way to get 5.1 surround sound in digital mode is buy a creative speaker system, it uses digital din connectors. dvd's will work though obviously as it uses ac3 as apposed to creative's encoding but you'll only get 2 speakers for anything else.
If you don't care about digital or use soundstorm or something then it's fine.