One thing to note is that the higher the sample rate of the mp3 (or whatever) file, the more work the CPU will have to *decode* it. This means that while an 11.025kHz file will need a bit of CPU to convert to 44.1 or 48 kHz, that will be swamped out by the actual decoding needing a lot less.
What *may* make a difference in quality is setting the sample rate to a multiple of your podcasts (if possible), e.g. set it to 44.1kHz if you listen to 11.025kHz or 22.05kHz stuff, and set it to 48kHz if you listen to 12kHz or 16kHz files. As saratoga noted though, you're starting with fairly low quality, so I suspect you probably wouldn't hear the difference anyway.