With what you want to do I would go for a laptop in the entertainment grouping.
For example HP have a whole series of laptops with the "entertainment" label (I am just using HP as an example, Toshiba, Acer etc probably also have their entertainment laptops.)
These are usually built with better screens, better speakers and so on.
If you see this HP page you can see that they have a number of entertainment laptops:
http://h10010.www1.hp.com/wwpc/uk/en/ho/WF02a/ 21675-38187-38191.html