If you want an experience similar to how the movie was intended to be watched then you definitely need a couple thousand. Most movies are filmed in 4K, so you need a proper projector and screen size to even see a difference in resolution (I’d say 100 inch minimum). Then you need a Dolby Atmos setup with a compatible receiver too. 5.1 won’t cut it with most movies. It’s definitely worth it if you can afford it. But if you can’t afford it, a theatre is still the only way.