If you already have an A520 and your TV has a composite input--it should if it has s-video--you may find that your TV's built-in scaler and deinterlacer are more than adequate for fun on the A500. The other options suggested will provide a better overall display experience, but don't spend money unless 1) you're not satisfied with your current experience or 2) you're sick like the rest of us and need to spend money on Amiga gear to survive.
