Scott549 and
Simplicated are absolutely right on the quality question - it's impossible to put back information that was earlier thrown away.
As for legal lossless music, the only "major" store I'm aware of is
hdtracks.com, but obviously their selection is very limited compared to iTunes or Amazon. I've also seen lossless music on artist-specific stores at musictoday.com, but unfortunately going to the main site there redirects to Ticketmaster/LiveNation.
😱
Sure would be nice if Apple offered lossless... it's not like it'd take any more bandwidth than all the movies and TV they sell/rent, and I'd finally be able to stop buying CDs that clutter up my closets.