I'm a lossless audio guy, and you are not going to notice the difference between an MP3 and lossless audio file unless you have top quality headphones/speakers. If you have those then you will notice a huge difference.
I was in Chicago visiting my family for Christmas. I rented an HD movie from the iTunes store and it took over an hour just to buffer it. Turns out my uncle only had 3mb down and 1 up. Paltry! At that rate the movie would have kept buffering.