Hi,
What do you mean by poor quality? Has the picture changed or is it just not playing back smoothly? You may need to render parts of the sequence to see what the final result will look like. Use the work area bar above the timeline to select how much you want to render then hit ‘enter’ or go to the ‘sequence’ menu and click on ‘render work area’ (think that’s where it is – trying to do this from memory!). Hope that helps.
cheers – James