Below is my home layout. I've got most things setup the way I want. To get the line-in on my mini to play through the speakers (the TV) I am currently using LineIn. This works and does exactly what I want, but it has a window thats always open. Is there a background application or service that I can have always run that will do the same thing?
I know there is AirFoil but it does way more than I need or want. I just want a simple Line-In to speaker passthrough that runs in the background. Ideally even when a user is not logged in.

(yes lots of extra stuff in the picture, I got tired of making small specific pictures and just made one for everything)