We're looking at putting a site on a hosting package with VPS.NET. The reason we're going down this road it because of the simplicity of taking snapshots of the system and restoring them if needs be - also the host has systems in the UK and US.
But what sort of level should we consider as a basic level hosting system for SS based upon the options that are offered by VPS.NET?
Just like any hosting it does depend what type of site you are hosting. If they are small you can get away with the lowest vps plan they offer. For some of my clients I run 5/6 sites on 1 VPS with 256mb Ram, HDD space is never an issue with hosting these days (my average install of SS is only be around 250mb-400mb once you take images, uploads into consideration) and their cheapest plan offers 10gb so you should be fine.
The main thing with hosting SS (and most large app's/sites) is memory usage. Get as much of it as you can but if you are unsure then start off at the cheapest plan (256mb) and if you notice the performance becoming an issue then simply upgrade the plan :D.