My suggestions: Endless sorrow because the single mix is much better than the album version (IMO). & for "theme of a-nation '03". vogue for "ever free". Depend on you for "Two of us".
I was going to suggest exactly these. They all have either b-sides (&, vogue, Depend on you) that are worth buying the single for, or a title track in a version that's better than the version that appeared on the album (Endless sorrow). I'd say go for these.