Why not just use an Amazon server? A micro-instance is around $6 a month and if you need more, it would only take an hour to get yourself onto a larger instance. We were getting 15 – 20,000 visitors a month while running Drupal. Still tweaking Wordpress, but apparently with a bit of server mods, its capable of handling 1500 requests a second.
Side note – A 5MB database might be okay with a small wordpress, but would be destroyed if you were using Drupal or Joomla.