I do something similar to OP but do the final transcoding to HE-AAC VBR 64kbps (ffmpeg params `-c:a aac_at -profile:a 4 -b:a 64k -aac_at_mode 2`). The tracks sound more than acceptable to me and this way I can easily store my entire collection (+80k tracks) into my iPhone. Modern codecs are wonderfully efficient.
Thanks for sharing your params... This is nice, maybe that's something I should consider. I need to test wether my car supports aac. My ipod does and kitchen radio is not that important.
You should See my audio books workflow with m4b-tool and audiobookshelf, which is probably even better ;)
Did you know ffmpeg has a non free Encoder (libfdk_AAC) thats sounds slightly better?