[BNM] Hosting advice

[Ali]

Hi

I am developing a small viral quiz (legit and spam free) that will be notified to approx 400,000 subscribers and have share tools on the page. This makes my alarm bells ring with respect to server load when asked to host it. 

The quiz will be very lightweight, low on graphics and be an innerHTML type of refreshless page with the browser doing all the work. My fears relate to potentially thousands of concurrent users on the server, I only run a cheap'n'cheerful  VPS - anyone know what type of spec is required for the hosting of this and who specialises in this? Am I panicking unnecessarily?

TIA

Ali