I grew up with .shn for grateful dead shows, ripping CDs to .Flac with EAC. I'm familiar with m4p, mp3, ogg, aiff. also sacd's and dvd-a's. I read in this site that audio quality, source and playback a a big factor. I believe that a 24bit-192khz flac version of an album is as good as you can get for playback. Right? I was looking at the AK240 and it seems like there are a lot more playback-file considerations other than playing back flac on an ipod.
24 bit 192 kHz flac is a very high resolution indeed. Even though the differences with 16 bit 44.1 kHz (CD-quality) are often minimal and sometimes nonexistent (when 16 bit files are upsampled), there has been research that seems to indicate that trained listeners can pick up a slight difference in a double blind test in a controlled environment. This research has not been replicated by other scientists yet, so it's no scientific proof yet.
A much more significant difference is the quality of the mastering and recording. When there is only one version of a song, that's all you get and the best quality you will be able to enjoy. There are many songs and albums with more than one version. You might have read the advertisements that state that a song is "remastered" or "mastered for iTunes". Both sound positive, but the "remastered" songs are more often of poorer quality than the original master. The ones "mastered for iTunes" could be of netter quality, but not necessarily.
There have been developments in technology that have lead to masters being produced louder. To the human ear, louder is usually perceived as better, but that is a fake sense of quality. What often happens is that the dynamics in the music are taken away and nuances in the music disappear.
So basically, louder music sells better. Unless the RMS volume of the music is limited by law, the loud and crappy masters will keep existing. This development is called the 'loudness war'. There is much more information on it on this forum.
A well recorded, mastered and converted high bit-rate MP3 will sound clearly better than a poorly mastered 24 bit 192 kHz flac of the exact same song.
To illustrate my point, here are YouTube videos (not quite the best quality for playback) with on one side one of the worst mastered songs I have heard compared to a different song from the same band that was mastered much better:
