Totally agree with A-T-G, see if you can get a ball park figure (reminds me of a funny story which I'll save for another time...). I'm not certain, but I imagine different cuts cost less so you can get a higher quality?? maybe?? Okay, that's just a shot from the lip, but both of my rings have been round and I'm always comfortable with their "show" quality.
After you've narrowed it down to about three, take the lad with you and ask his opinion. (Don't want to scare him, but you might as well start in the process of letting him think his opinion counts.

)
Huge congratulations to you both. Enjoy this time, it's amazing.
C.