Wouldn't it make more sense to buy a non-hard drive based player that takes SD cards, now that SD cards are available with larger capacities?
I have the iPod Classic 7th Gen. It has a 160GB hard drive, fast USB 2.0 chipset, and a hard-drive interface. This means that loading songs is quick, rebuilding the music library is quick, and there is little lag between changing playlists, etc.
The non hard-drive based mp3 players tend to have a slower USB chipset or a slower processor. This makes loading songs take 5x as long, rebuilding or refreshing the music library takes 30 minutes or more, etc. For example, I have a Sansa Clip+ and just bought a new 64GB SDXC 90MB/s card (Black Friday deal). Transfers to and from the SDXC card using a USB 3.0 memory card reader is very quick. However, synching my full library plus podcasts (50GB of songs) for the first time through the Clip+ took all night (I just started it and went to bed). The point is that few of the memory based MP3 players were designed with the processing power to handle large libraries.
In addition, only iPods have full integration with most modern car head units (Playlists, art work, steering wheel control, etc.).