shared hosting with guarenteed resources?

[manvbf]

I've been waffling about shared hosting vs vps since with vps I can purchase exactly how much ram I ant, and different plans generally have different cpu limits available. But I don't want the work of managing a server, etc . . . I thought managed vps did this, but at least from what I've seen, managed vps just provides a web interface but you still have all sorts of extra administration to worry about.

Soo.. the next question is, is there a middle ground where you can guarantee and buy more resources as your sites grow, but as shared hosting?