Hi there,
the speakers in the MacBook aren't that powerfull so the output has been softned accordingly.
I presume you have turned up the volume in the System Preferences-->Sound to the maximum...
If that isn't loud enough then you may want to get an Airport express an then you can pipe the sounds through your HiFi as loud as you want...
You can also try connecting some external speakers with a preamp to see if that's better.
regards
Ric