well it is a given that if you are looking for high quality audio files, you'll want WMA or FLAC files. The issue with that though is that the source can sometimes not have a whole lot of quality. I'm referring to the trend in the studios to record "louder" and clipping some of the soundwave away to make room for that. There's already plenty of literature that explains it, google is your friend.
This is true, and it is an incredibly annoying trend. It especially shows when comparing any of my modern CDs to some older ones. I have some Pink Floyd disks with excellent quality, and they absolutely blow away almost any current album that I've heard.