When you buy a digital SLR, you're not just buying a camera. You're buying into a system, which consists of at least a body and a lens, potentially a lot more lenses and other accessories like flash.

If you think you'll go further in this hobby or profession or whatever, you should look at all those components. It won't do you any good if you buy a great body but you can't find the lens that fit you.

Each brand has its strength and weaknesses. Nikon and Canon are most popular brands with lots and lots of lenses and accessories, but neither has in-body stabilization. Olympus uses the "Four-Thirds" systems with smaller sensors, which allows them to make smaller and lighter lens and bodies, but that also means more digital noise at high ISO. And you also have Pentax and Sony, each with their particular features.

So, what are you actually trying to get for $1,800? You can get a Nikon D300 body, but you won't be able to take any pictures with it as you won't have any lens. Or you can go with a more basic body, and then various combination of lenses.