Source for low cost redbook CDs

I'm looking for any recommendations for good sources of CDs with a large inventory of music and reasonable or low purchase/shipping costs. Currently a member of www.yourmusic.com which offers a shipped CD for only $6, which seems to be the best I've found to date. Only problem is that they've got a somewhat limited inventory. I enjoy a wide variety of music - classical, alternative, christian, old and new rock etc. Any suggestions?