There's an extension for Google Chrome called "video downloadhelper' that can extract videos from NicoVideo, though the download speed is a bit slow. I recommend you install it.
Since I have a high-fidelity headphone system specifically for listening to music, I usually collect WAV files,
but for the average person, I think a bitrate of 128 kbps is more than sufficient for everyday listening. However, if the bitrate is 96 kbps or lower, I wouldn’t recommend collecting such files, as the sound quality is simply too poor.
I just tested it and the download was successful. I checked, and the audio quality is about 128 kbps—it sounds perfectly fine.
If you have the means in the future, you might want to consider upgrading to WAV format, but that would require a CD.
Video Download : transfer.it/t/XEbcT6ozlTzb