I pick up 4 or 5 saddles online each year. Ebay, newspaper ads, ranchworld.com. Just had a polo saddle delivered last night, in fact. Not a high end saddle, but I'm familiar with the brand, and it turned out the seller and I have mutual acquaintances.
I try to go for brands that are at least known. Some western saddles are used custom made and I ask my saddle making buddies what they know about the maker's work. Personally, I would take a saddle with more wear if I know the quality is good over a newer/less used lower quality saddle.
I've been fortunate and have not bought a crummy saddle yet. Good luck and have fun shopping.