Also based on personal experience, the Griffin PowerDock does work well with an e200v1:
- transmits audio through its line out port when in the Rockbox firmware (with the volume level being scroll-wheel dependent);
- charges when in RockBox firmware (I'm using RockBox v3.4)
Just hold the Select button while you drop the e200v1 into the dock.
However no such luck with e200v2 (Sansa AMS) - no audio. That's the case with RockBox AND the original firmware (which goes into "connected" mode). At least under RockBox charging works, unlike the original firmware which seems to go into a strange no-mans-land where it's "connected" but not fully, so doesn't enable charging.
I think based on this forum entry:
http://forums.rockbox.org/index.php?topic=22942.0the lack of audio is expected, and hopefjully will be fixed in the future.