Don't be too afraid of the entry level cameras from Nikon or canon. They are light years ahead of where you are and will, most likely, be good for you for years to come. Lenses are where you will want to spend your money anyways. And, as Dave and Chris mentioned, the kit lenses are good to start with but not always really good. You will want a true macro lens for really nice corals shots(warning; they are expensive) anyways.
As an example, I'm still using my D40 I purchased 2 years ago and haven't reached it's limits yet(except in low light situations which I don't really find myself too much anyways.) Do I _want_ a D90 or D7000? Yes. Do I really need it? No. Did I spend the same amount of money on two lenses that I did for the body plus two kit lenses to take great macros and general pics? Yes. Am I happy with the overall setup? Yup. And I bet most others would be satisfied with it too.
The other thing, to get really great photos, is it takes a really good computer behind the viewfinder first.