Thanks for the reply, Keith.
I actually use AE to make videos for my own music, for posting on the web. So, they don’t need to be broadcast quality; I just want them to be high enough quality for, say, 1080p on You Tube or Vimeo, for example.
I’m trying to find a good balance between file size and quality. I’ll try raising the bit-rate in the format options, like you said, but what codec would be best for my purposes (that would make reasonably high-quality output, but with smaller file-sizes)?