Sensor Size, High ISO, Wide Aperture Lens

Ideally you would get a camera that has a large sensor with good high ISO ability, and a lens with a wide aperture to let in more light. The previously mentioned Panasonic FZ200 has the lens, but it still has a "point-and-shoot" sized sensor. It's the least expensive option at about $600. Next up in quality would be a mirrorless camera, such as the Panasonic and Olympus "Micro Four Thirds" cameras. Those could be coupled with Panasonic's 35-100mm f/2.8 lens. The lens is $1500, so you would have to shop around to get a decent body and the lens for $2000. There's more lens selection with a DSLR; a 70-200mm f/2.8 can be had for under $1000 (the top end ones are more than $2000).