I received the refurbished Dell-branded 5300 card today and it installed without a hitch and is working with two antennae right now. I'll probably install the third one eventually.
It looks like you can take your chances with the Chinese imports and maybe get a card that works and maybe not, or you can pay more (mine was just under $40 including shipping) and get a card that works without a hitch. I got three cards that would not work in my Mini 9 (one from China and two from a US seller, but not Dell cards, and nothing in the description warning that they might not work in all brands of computers) before getting this one that did.
I won't know whether the 5300 card works better than the original Broadcom card until early April, when I travel to a place with a spotty connection.