[giberson]

Here's an idea that I'd like you to try first. Pay what you want subscriptions. Offer a subscription service that is completely voluntary. Do not label it a donation system. It is simply a subscription service. People will pay an amount of their own choosing to support the site. Offer monthly and yearly subscription packages. See what happens. I bet you will get a significant conversion rate to paid members, all whom enjoy and want to continue using your service.