What's the Plural of Prius? Help us answer the question

This July, the existing 2012 Toyota Prius is joined by the seven-seat Toyota Prius+ and the new Toyota Prius Plug-in hybrid, the most advanced road car we have ever made. But while this is great news for Toyota hybrid fans, it's posing us a problem. Exactly what is the plural of Prius? What should you call a line-up of all three cars? We need your help to answer this difficult question, and have launched a new, simple to use, app on Facebook to record your thoughts. Vote now at   / toyotauk