The big downside to this device (X5) is that it can only record to MP3, not to PCM wav.
I would rather recommend the Archos Gmini 400, it can take a line-in and record
to either ADPCM or PCM Wav *of course only the latter is desirable*
However,
the Gmini's line-in adjustment of recording levels is not by gain adjustment,
but rather by digital attenuation. Hence, I would recommend a mic-preamp
to go with the Gmini.