I generally do sentimental gifts for birthdays/anniversaries and things in that nature. It's definitely different with the engagement ring. It's been clear that she would be extremely happy if it's over 2.0 cts, and why wouldn't you want to make your SO the happiest person the world? Especially if you can afford it. I would've bought the ring earlier, however I wanted to ensure that I had a decent amount in assets as cushion.
I guess my rant was more about the strong marketing campaign that the diamond industry had instilled into our social norms. When viewing diamonds in person, I just so startled something so small can be worth so much with absolutely no value-add.