It appears sufficient for now as a starter website, just stick with your plan for now, but when you get more traffic in the future then you will need a dedicated server to deliver high speed performance. After you can compare with S3 plans (just media or the entire server)
The equation is simple: more traffic ==> more revenue from ads/sponsors ==> you can afford better services for your traffic.
But never ever put lot of money in the beginning, invest as you go, with this strategy you avoid bleeding cash in the first experiences. Good Luck