I use a Schiit Bifrost to play my streaming music, and I have to say that sometimes I prefer it to CD's. I love the ease and accessibility of streaming music. I can also audition albums that I would ordinarily would not have considered purchasing.
To date, I am using Pandora, Spotify, and Classics Online.
As marktomaras points out, you can also rip your collection to hard drive.
I purchased JRiver for that task and I like it, too.