Boutique Downloads
Think of the major online music retailers as the love-all-serve-all method - iTunes and Amazon stock a whole bunch of music and hope to drag in as many folks as possible. They function as content gateways in that they have a limited "stock," if you will, but that stock is probably both wider (broader range of artists) and deeper (always more copies of the same thing available) than the average record store. Still, aside from celebrity playlist or online recommendations, there's a supermarket feel to it. Just find what you want on the shelf and buy it.
I'm intrigued by the new Wax Poetics digital store as another alternative to that. With a respected brand name and the willingness to seek out older and out-of-print material, they can make a respectable niche for themselves fulfilling needs to more particular music listeners. I'm hoping this will turn into a virtual Dusty Groove for downloads.
Except that Wax Poetic only has one James Blood Ulmer album, which is what I always seem to walk out of Dusty Groove with whenever I'm there.