Playlists & Cleaning up tracks (and a little bit of rockbox)

I'm trying to come up with a generic solution for my playlists. Here's the problems:

1) I'm in the middle of getting rid of a lot of dupes, and cleaning up my music, so, I may have delete, and re-create my library. (Music lives on a NAS)

2) Sometimes I run my ipod as a Rockbox, and it only supports m3u playlists.

So -- what I'm wondering is -- is there a m3u to iTunes playlist converter? That may solve my problems, by letting me maintain my m3u files (or create them in iTunes, then create m3u's based on them)

Or -- does anyone have a better solution that will let me both keep my playlists after a library rebuild, and, let me have some of the playlists on my ipod, when in rockbox mode? (I also have an iPhone, so I need apple playlists too)

Thanks in advance!