Server host that can grow with my site?

[How?]

I'm launching a WordPress site next month that I believe will grow faster than expected. I'm not sure what's the best choice for hosting. I currently have a VPS host (who I really like as a host - they're local with killer support) and I'm not sure if that's the best route or not. My current VPS (12gb ram) has multiple failures a day with automatic restarts. It's hosting a one multisite install (with 3 active subsites, 4-5 inactive subsites and less than 100 visitors a day total on average), a second site with 60-70 visitors a day and 2 other sites that are lucky to get one visitor a day. The failures have me concerned that 1 site 300-500 members and 1000 hits a day will need a lot more resource-wise than what I have now. I don't think that there's that huge a load on it (though maybe the multisite is a resource hog?). So I'm really not sure which way to go - and perhaps it's because I don't understand hosting that well. A distributed grid sounds cool, but does it work in practice? Is eventually getting a dedicated server unavoidable? What the hell do sites that have a lot of members and traffic do?

What can you say about Neironvps.com dedicated servers for rent hosting? Any reviews? Other hosts?
All advice will be appreciated - I'm planning on launching my site, I need to get this squared away ASAP. Thanks!