212681 - no, overly thick girdle hiding weight - RBs are so common it's easy to do better
214502 - numbers look good, can your vendor get you any more info/pics? And/or can you go see the stone/have it shipped out to inspect yourself?
613738 & 712648 - if you are considering having some stones called in and you'll have to pay return shipping, probably wouldn't bother. If they're already in-house have them look them over and give you a review, and get some pics/more info.
I assume you went to the dealer to look at the diamonds. Did the dealer give you any reason why Diamond B and D was more expensive than C?
From the looks of it, Diamond C has a better color than B and D. Additionally, Diamond D only had an very good cut and Diamond C has a excellent cut? Is Diamond C not eye clean?
Diamond B and D are from a different jeweler that A and C. I think they are way marked up in my opinion but I cant get A and C to come down at all!
Diamond C is eye clean but it does have quite a few inclusions.
Diamond A is not eye clean.
Diamond B is eye clean. Should the Med Blue Flour worry me here being an F in color?
Diamond D is eye clean.
It amazings me to see the clarity on B,C,D all SI1 but their inclusions vary so much. Im just not sure which direction to go. For the money is C the best stone being a D? If it is eye clean is that all that really matters besides all the inclusions the "certs" show?