I would guess that your definition of "old" should be clarified. If you mean your present speakers which are due for replacement - they can be utilized as your budget dictates. If your definition is more towards relics or antiques, they probably would be difficult to properly integrate sonically with modern speakers.
You mention leaving "them" for inclusion in an audio system. This again would assume you place little value on reproduction of music. If they are not good enough for HT applications, they would be even less desirable for music applications.