Which Model Train should I get?

My dad used to collect model trains when he was little and he always talks about them out of nowhere. I would ask my aunt to send them out to him as a surprise but I don't want her to go through the trouble of going to their childhood home and looking for them in the attic or wherever they might be. I know nothing about model trains but I want to buy my dad a nice train set to surprise him just because I love him. Can you please suggest me a nice train set for a reasonable price (hopefully around $150) that will most likely impress a man that used to have hundreds of model trains with towns? I would really appreciate it, thank you.