I use an Archos JBMM 20 all the time for recording using a Behringer UB1222FX Pro. I use the headphone output of the mixer connected to the line-in of the Archos.. (didn't really like the results from using the RCA outputs).
The JBMM records the analogue signal as an mp3. Not sure about the AV400, but I think it records as WAV files.
Personally, I wouldn't recommend Archos products to anyone... but if you have one already, do not rely on any data on it being safe.... make sure you have it backed up onto more reliable media, or you will lose it!
Here's a couple of examples of recordings I have made using the JBMM:
http://singersshowcase.com/song.php?id= ... act2=82873
http://singersshowcase.com/song.php?id= ... act2=82807
If you wanted to record to a laptop, you could connect it in the same way using the laptop's line-in connection. Running Adobe Audition, Cool Edit or similar software would enable easy recording. You could also record using the built-in Windows Recorder but I'm not sure how good that would be.