Where do you buy good CD recordings?

What are the recommended web sites for buying CD’s? I noticed that some sites (like www.hdtracks.com) provide music to download (AIFF Format). What is your experience in downloading music? I like the www.referencerecordings.com web site and am looking for other similar sources. Are there any stores that you recommend for buying music? I am interesting in looking at a list of CD’s to include a brief description and some sample songs to listen to before I make a purchase.