Hi Steve-it depends on what you are looking for. I would recommend different vendors for different shapes (some specialize in rounds/cushions/etc.) If I remember correctly you are looking for a princess? The problem with BlueNile (and possibly adiamor as well, do not know much about them) is that they are a drop-shipper so the diamonds are not in-house, and they cannot provide images or ASET images.
for princess cuts I would recommend (in no particular order)
High performance diamonds (crafted by infinity princess)
Whiteflash (ACA or ES)
Good Old Gold (signature, solasfera, or other nonbranded princess with good ASET)
Brian Gavin Diamonds (signature princess)
James Allen (have to weed through inventory, can request up to 3 ASET images)