Hinkletown sewing machine has a pretty decent amount of aurifil. Good prices, too. It's located on the owner's farm. They have a very large selection of Isacord, too. I live in the area and I think they have the biggest selection that I know of. Here's their info: Hinkletown Sewing Machine Shop, 232 Wanner Rd., Ephrata, PA 17522. 717-354-0204.
Also, Green Fairy Quilts (online) is having a sale on aurifil thread.