Datacenters are the place to go for high speed, high bandwidth with 100% control over your own hardware, OS, etc....
Datacenters will provide physical space, power, connectivity, and support all in a redundantly cooled, fire-suppressed, powered, and secured facility. There are various plans, generally offered by amount of rack space and speed & bandwidth.
Your desired port speed and bandwidth cap will all depend on how many users connect simultaneously and how much data they will transfer both ways and how fast you want their data to transfer. There's no real way to figure this out except to guestimate, put the server and service up, and see from first hand experience what will work and what won't work.
Good luck.