A good surround sound system turns your living room into a proper cinema and lasts for a good ten years if you buy the right gear. You want a setup that handles movies and music cleanly without needing an upgrade next year.
Aim for the end-of-year electronics sales when retailers clear out shelf space. That is usually when last year's receiver and speaker models drop in price while still offering the same exact sound quality.
That intro window is a deadline, not free money, so if you still have a balance left when the 18 months are up, standard interest rates kick in fast.