Try this for some historic data, you have cpanel there right?
https://forums.cpanel.net/resources/...x-servers.379/ I would say lets start with something like a semi dedicated as here
https://www.hawkhost.com/semi-dedicated-hosting or we can even try professional shared (yuk I know) to see how much we actually use realistically, we dont see a thousand members all active on the board at the same time. I am happy to chip in half if you want to cover the other half.