You can "up-sample" files to higher quality... Doesn't make them better, just takes up more file size.
You are either saving directly as MP3, or saving as WAV then converting to MP3.
In the first example, what are your settings while saving the MP3?
In the second example, what are the settings for the WAV? Then what are the settings you're using for the MP3?
You can save a nice economic .WAV format then screw the pooch on the .MP3 conversion and (possibly) make it big again.