It's too bad that there aren't more options like this, then you wouldn't need a pre-amp at all.

http://www.casatunes.com/products/xli.html

I read a review of the software and it seems like it can't do Pandora. Also, a higher quality output would also be nice, but Casatunes seems to be the only option like this that I could find. It's too bad Apple doesn't get into this so that we could get a nice intuitive solution. If we could get a high quality sound card with the ability to send different sources to each room with nice easy to use software at around the price Casatunes is selling this for, then it would be the goto solution for a whole house audio hub.