[Mauzen]

Actually you cant say anything about the amount of players or whatever. "2.0+ ghz" cpu says absolutely nothing about the performance. Even for real pcs the cpu frequency doesnt say a lot about that, now this is a virtual one with handsful of other limitations . So its impossible to even say a rough estimate. It could be like anything between 5 players to 200 (with tendency rather to 5), greatly depending on the script you run. Some scripts might even push the "2.0ghz" cpu to its limits with no players online at all.
For VPS youll always have to test how much power it got. Theres no useful feedback anyone could give you about that, except that 256mb ram are barely enough for a small sever, and 768mb are enough for all servers.