Just wanted to jump in and give my 2c worth on proven donors. We wanted to go with one, like everyone does, and attempted to at one stage. The agency advised that she had great eggs, had done 3 cycles, always got 5 day blasts and that resulted in one pregnancy. I checked with CFC and they advised that she'd actually done 6, there was one pregnancy and that was miscarried, and there was one frostie. When I challenged the agency on this they said they only know what the donor tells them.
So, if you really feel a connection with someone and they're not proven then don't feel you have to rule them out. They could be fantastic. I would just say, do your due diligence, get their AMH tested, ask the agency and CFC about their history. CFC will tell you to not go ahead if they had any doubts. They did for us when another donor we selected had a low AMH.