I've used Nikon, Panasonic, Olympus, and Canon in the same price range. I've played with the Sonys.
For consumer cameras, they'll all give functionally comparable results if you shoot RAW (a few years ago the Sony sensors in Nikon, Olympus, Sony were a little bit better, but even now that difference seems to have leveled). I'm told that there are differences in JPEG processing, but I don't know because I've never shot in camera JPEG .
I'd go to Best Buy or your choice of (rapidly disappearing) local store, and pick the one you like the feel of the best. Note that there's been a lot of over production in these lower price ranges, so previous years models can be had new in box for much less (check out B&H, Adorama, or especially Cameta Camera).
For photographing my tank, I'd get the 18-xx mm lens that comes with the camera (14-45 for Olympus or Panasonic), and then a macro lens - either the 85mm lens or the 105. (The Olympus 60mm is a great macro, and general purpose, lens for Panasonic and Olympus).
For wildlife or sports, D300 or 7D (though the D7xxx or x0D will also do well) plus long lenses.....