iphoto settings for best quality small quicktime movie

Hello,
I recently shot a wedding and would like to make a quicktime slideshow for the web.
I have done this before on my 4 year old powerbook and the iphoto that came with it and just go a new macbook pro with the most current iphoto.
I made a slideshow and then went to export it but the quality is always looking super poor.
I wanted the size to be between 320/240 or 640/480....I clicked on custom settings and tried a few different options but none of them seemed to give me a crisp video at the small size I wanted (there were a lot of options I did not know about either though).
Can anyone give me the exact options I should trip in iphoto custom settings to get a great quality video in a small size like that?
It will be for the web so I'm not sure if I should chose m4v or quicktime movie (quicktime is what I used before with the .mov)....cany anyone help guide me along in this? the iphoto tutorials did not help much.
thanks,
M