currently available will fit your bill, except when it comes to 'good sound'.
I have three laptops which I use in the coursae of my work. All of them are relatively new, and although they all have built-in speakers I certainly wouldn't class the sound quality as 'good'. It's average, and to get better quality you'll need external speakers.
Laptops don't have the hard drive capacity of desktop machines in terms of space, but you can use memory sticks if you need more space.