"Big enough" is a relative term. What one person considers huge, another person may consider average. It depends on the people, the area they live in (or even the country they live in), their relative social position, etc. Many very, very wealthy women around here wear no diamonds on their fingers at all, as they have no need to ostentatiously display their wealth.
So no one else can answer, for you, what is "big enough". As far as I am concerned, a diamond is an afterthought. No stone can possibly represent what my dh and I have, and I have seen amazing gorgeous rings of all shapes and sizes.
This is exactly what I was trying to say. The size of the ring doesn't really matter. It isn't a contest. Love is what matters most.