Cut is the most important but I would suggest you first try on a 3ctw pair. I currently have a 2ctw pair (1ct each ear) and I thought I wanted to upgrade to 3ctw. I went shopping to first to try on for size and decided they were too big. They did not look good on my earlobes and drooped due to the weight. I tried it with the larger screw backs but they still did not look good and I felt I was forcing myself to make it look good. The SA actually did say he thought my 2ctw looked better so that's actually when I told myself bigger is not better and skip the upgrade.
Also, if you are considering 3ctw or even 2ctw, you may want to look at loose diamonds which is what I did. I looked all over and ended up buying two loose diamonds from Hearts On Fire that were perfectly cut and had so much fire. I mounted those and it was easy. Also be sure each diamond has a GIA report. You are effectively buying diamonds that many people would have as engagements rings so you should research each stone.
Good luck to you and congrats!