As for the main which camera to buy question, the fact of the matter is that any, and I do mean any, DSLR that you can buy new is perfectly capable of taking stunning 12"x18" (biggest size I can get at CostCo) or 13"x19" (biggest size you can print on a consumer photo printer). Yes, some have better high ISO performance, and some have better auto focus, etc, but for now that's really beside the point. So what you need to do is figure out two things. What lenses/flashes/accessories do you want to go with your camera, and which camera feels right in your hand/has a control layout that makes sense to you.
And because no one else has mentioned them (or at least I got lazy and didn't read it), you might want to take a look at the micro 4/3 from Olympus and Panasonic and the Sony NEX cameras. They are mirrorless interchangeable lens cameras that give you some of the benefits of DSLRs while not giving you all of the bulk.