You might want to consider saving a bit more to jump into the DSLR world. Quality lenses will be a good focus. I've just got kit lenses and I'm itching to get some sharper lenses.
My only experience is with T3i, but I think it's great for a beginning DSLR. I didn't think I'd use a fold-out LCD screen much, but I use it all the time; very handy! The T3i is also awesome if you want to do any videography too, especially if you add Magic Lantern to the mix.
Also, are you planning on doing a lot of aquarium photography? A nice macro lens can cost several hundred dollars, and you're going to want a flash that you can use wirelessly from your camera; maybe even more than one. A flash system shooting down from the top of your tank is how a lot of the best photography on this forum is shot.