A proper surround setup (5.1 is more than enough for a mid-size room) or even Atmos speakers can be had for a reasonable price if you shop around. There's really no substitute (in my opinion) for the experience if you watch movies and have a compatible receiver/amplifier. A large and well-designed subwoofer is incredibly noticeable as well depending on your use case. It can easily sound better than the large majority of seats in your average theater which aren't ideally positioned without spending too much.