If you are on a budget, what you are looking for are "SEO Servers" or "SEO VPS"
They are tiny VPS, each on a different IP address. I saw some at Web Hosting Talk. If I remember they were $1 or $1.50 each, per month. Only a little more than just renting the IP addresses. You will probably need the Wordpress plugin "Manage WP" to manage all those tiny VPS's or it will drive you crazy.
Sincerely,
TheEye