From what I've been reading through the years, ultra high contrast projectors like the 5020 show their quality mainly only in a light controlled theater room. If your walls or ceiling are painted white or if you have light coming into the theater room at all, it will be hard to justify the additional cost of the 5020 over the 3020. Probably also, if you are new to projectors, it will be harder to appreciate the additional quality of the 5020 over the 3020, because both (and many competing models) give such impressively good pictures anyway.
Many of us would recommend a surround sound system perhaps even with multiple subwoofers before springing for the very best projector you could buy, if you don't already have one. But, in a choice between special seats vs. better projector, I'd sure recommend the better projector if you have a light controlled room.