Agency References?

I've been thinking about visiting agencies a bit more. I already have one that I go to. However some of the higher end ones require references.

Now, the few agencies I've been visiting and the ones I want to visit involve contacting a handler who then refers me to the provider. Anyone had any luck getting references from agencies where you meet providers through a handler? Is that even reliable? I also don't see why an agency would give me a reference to go give business to another agency. Anybody have any thoughts or experience with this?