HDtracks is not cheap but they do have promotions quite often and it's common to save 15%. It's not much but it does add up. I am however very selective with what I get in order to keep costs down.
I don't much listen to music any more at home, my equipment is primarily for movie watching but I do have a nice small selection of mostly Jazz that I like to play from time to time and it is awesome to listen to.
Another great place for high quality digital recordings is http://www.chesky.com.
I have picked up a few from there.