What is the proprietry software included with the MP3 player ? – it is an optional sound editor.

Does the line in MP3 player recorder take both a powered (preamp) or an unpowered microphone? Either

Does the recorder read the open source formats i.e. OggVorbis the wiki editing code. YES!

With regards the interface, other than reading the reviews or previewing the equipment by buying locally this is hard to answer.