Thanks for posting that. Now that you know what's really happening you can focus your attention on other things to help optimize your setup.
There's a Sansa Runtime page
on the Wiki. You may want to add your results there.
The response to questions like yours is pretty much what what you got. If you believe there's a difference run the appropriate standardized test and report the results. I've done the same with a number of items I thought I'd observed and found sometimes I was right and others I was wrong. The important part for me was that I knew for sure what happening rather than guessing.