It really depends on what you are shooting and how deep your pockets are. For Portrait work you can go for something cheaper as long as you do not want to print huge prints. Commercial work such as Product and Fashion will require Full Frame and larger Filesizes.
Canon brought out a great new Midrange camera the 6D Read More on here. If you are serious about your photography you should always consider Fullframe these days. If you have deeper pockets and dont have to watch your budget I would go for the Canon 5D. This is a real professional grade camera with full frame. The 1D Mark X is the Flagship, but I personally dont see the point in a big camera like that.
Another option will be the 700D which was just anounced. Not yet avaialble but will be a good camera to start with.
Always keep in mind that the camera is not as important as the Glass. If you are on a budget I would always go for the cheaper camera and spend more on the lens. Make sure the lenses are compatible with full frame. YOu can use those on the DX sensors but not vis versa without losing Megapixels.