Want to create smart playlist where song titles match names in another playlist, but w/ diff. bitrate
For a portable device using headphones in a non-analytical environment, I'd just sync them at 128 kbps AAC.
You're really unlikely to notice. 

You can do that in iTunes/[device]/summary in the last section, Options. It does that on the fly at sync [so takes a long time, first time] &amp; keeps your iTunes at full rez, using copies to send to the portable device. You can set this separately for each device you sync, the low-bitrate dupes are kept in your iTunes Library once converted, but iTunes always plays the highest rate available.  

It's effectively seamless



As a more generalised comment, &amp; speaking as a professional sound engineer, I don't think tracks ripped from CD are worth saving at anything higher than 320kbps AAC*. Much as they were vaunted as being the 'perfect solution' for audio... in the 80's... they really don't have all that much data in them to benefit from anything above 320.

*or FLAC, but as iTunes doesn't handle FLAC, that point is moot.