Speakers sound fine here. CD ripped music in iTunes.
Where did you get your music?
Also screen position is a factor. The macbook speakers are just behind the screen, the sound will bounce off the screen producing a surround sound effect. If your screen is down a bit this will not work as well.
Or so I understand it anyway.
I'm guessing you have upped the volume keys on your keyboard. I know its a stupid question but you are a new user.
And yes VLC is much louder. iTunes limits sound because some retards sued Apple because the loud noise busted their ears.
One last thing, if you have been listening noise for a while before, even something simple such as TV or talking to someone, or somewhere with a lot of background noise, they will sound quite. I tend to sit in a silent room before listening. Just like when using photoshop you are meant to take a break every half hour or so to refresh your colour palette.