I personally buy stock from Allen, though never an armored skink. The animals I have gotten from him are in excellent health and I love them all. He's also a good source for information if you need care requirements and tips.
As for underground reptiles, I've never bought from them but I've never heard anything bad about the quality of his animals, just that his prices widely vary depending on where he's advertising (and that it can be on the high side sometimes).