Ibook g4 with OS Leopard help?

I have an ibook g4 made in late 2005 with 1.33Ghz and 512mbs of RAM. I have been looking around and have found that 512mb isn't enough RAM to have OS x leopard run smoothly. I am looking at a 512mb stick of RAM on ebay, and I was wondering if I installed this that it would allow Leopard to run smooth. Or would 1.5 gbs of RAM be even better? Is there a considerable difference between 1gb and 1.5gb? Thank you.