Yay! A Silver Mt. Zion is basically the best band.
My two favorite albums by a Silver Mt. Zion are their newest, 13 Blues for Thirteen Moons and He Has Left Us Alone..., their first album. Their first is very spare and minimalistic, and completely unlike Horses in the Sky. It's a fine album, but if you started with Horses in the Sky I would go with 13 Blues for Thirteen Moons. Its a much angrier, louder record and kind of has a '70s blues metal tinge to it.