I am no genius but let’s think about this logically, shall we? You have a cd of perfect quality. You put it to mp3 form at 128 kBPS and shrink the quality. Then when you blow up the file again to full size would you expect to have full quality again? NO. It is the same with a picture on your computer. You can click and drag and make it bigger but in turn you are just filling the space with duplicate pixels. Upconverting, IMHO simply fills in the missing spots with duplicate data.
