Why are you looking to change from VPS to a server if you are currently on a server? It all depends on your site’s needs I suppose. If you need a lot of resources, then go for a dedicated server and expand from there. If your site is relatively small, go with a cloud solution.
A good managed provider will know what to ask you and based off of your feedback will give you something that will fit within your budget as well as be scalable down the road.
I am not sure if anyone asked you this, but what are you currently paying for your server and what is your budget realistically?