Great idea! Remember that the distortion caused by poor samplerate conversion is in the range that might be considered "subtle" for some people unaccustomed to listening for audio quality. Make sure to use an MP3 which would clearly show the distortion to your ears. For instance, songs with distorted guitars are probably not good for this test. Better if it's something clean, like a quiet acoustic piano piece with a lot of long note decays, or a solo a-capella vocal with some nice held-out vowels. And it should be something you know well, so that the difference would be noticeable to you.