How to improve audio output (s/pdif, sound card, other?).

Hello.

I am interested in improving computer sound output. I currently have an old, home-made desktop; my partner has a Dell Inspiron 1525 laptop. I have read that the best way to transfer audio output to an amplifier, for example, is via an s/pdif output. I wonder whether it might be worth buying a computer with an s/pdif output, and whether anybody can advise which mid-range laptop (maximum