The best replacement for rockbox is ipod linux.

The best alternatives to rockbox are rated as following:
★★★★★  ipod linux
★★  sansa firmware
★  sansa clip
★  podzilla
  ipod firmware
  landgraff
  apple firmware
  linux ipod

Your alternative for rockbox is not listed? Suggest!
Speaking about rockbox, one probably shouldn't forget about psgroove.

Other search terms related to rockbox and their ratings are:
★★★★★ psgroove
★★ doom
★ sansa clip zip
You have in mind a companion for rockbox and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of rockbox in all years. Click on graph for more.
rockbox
ipod linux
sansa firmware