I can't help with Freeware, but my preferred player on the PC, J River Media Center, also does duty of syncing to a handheld device (Android phone, USB drive, etc.) while converting to another specified format on the fly (just as iTunes can do with an iDevice, up to 256kbps).
This negates the hassle of manually maintaining separate copies and automatically keeps you up to date without having to remember to convert newly added files. I use 320kbps MP3 for the car, and the conversion options also allow you to perform any other DSP functions, such as level boost or equalization.
Using a sync function also allows you to sync to static or smart playlists, if you don't want to sync the entire library.
A cache folder is maintained on the computer, so that any new syncs of previously synced files are copied over without conversion being required each time.
I played with MediaMonkey MusicBee, which has a similar option, but it was not able to recognize all of my AIFF files ..... if you have no AIFF files, it may work for you.
Steve