Jeremy,
I would say that the only reason you have to go with a dslr is if you are somewhat serious about photography. I came to the same crossroad you are right now a couple of years ago, I chose the dslr as a long term investment, not just for taking pics of corals, but for everything (my travels, family and friends, portraits, art, fashion, etc. That's why today I have over $4,000 in camera and lenses as well as flash. I don't regret it cause I really love photography, but not everyone shares this kind of love. Before ever using a dslr I also was using a cheap p&s and got decent results like mothra posted, in fact before my dslr, I had a $200 camera that was given to me after it was a year old. I didn't pay for it, but I got the pictures I needed to sell all my frags, and had no complaints from anyone that they couldn't determine what they were buying from my pictures. Anyway, that's my 2 cents, I'm trying not to repeat what everyone has already said. Hope this helps.