To your question about downloading from iTunes, if your interest is in getting the best possible sound quality and you have the option of ripping the same music from a CD, yes, it's a bad idea to download from iTunes. All iTunes music is in lossy, compressed format and won't sound as good in a high-resolution system.
On the other hand, the selection in iTunes is huge and for lots of uses the quality is just fine.
On the other hand, the selection in iTunes is huge and for lots of uses the quality is just fine.