Rule number one: Don't mess with perfection.
What you have looks fine to me, and I hope you keep them natural. Obviously your husband feels the same. You should keep him, too.
http://www.paulkienitz.net/no-implants.html Beware of gross pictures (gross artificial boobs and gross boob job complications) This one's maybe a bit over-scary, but it gets a little into the mind-set, too.
http://www.kariwuhrer.net/glamourmag.html A semi-famous actress's thoughts & experiences.
http://www.domai.com/text/quality/index.html A before/after look. Tragic, IMHO.