There are so many worms in this particular can! I understand your frustration but the first thing you need to decide is what you REALLY want to make. The machine you linked to says it's only good for wood and plastics and not for tools over 6mm diameter. If you can stick to this yourself then some relaxation of your required specification is possible. A big influence on cost is also the cutting area as you've already realised. Do you really need to cut out parts the size of a whole sheet?
Do you want to make decorative bass relief panels, house signs and relief maps of New Zealand (Google 'CNC Nutz' if you do) or parts that need to fit accurately together with minimal hand finishing? This will affect the kind of accuracy you will ultimately need and, as a separate subject but just as important, how much you may want to spend on design software.

Good luck with your journey of discovery and don't be affraid to carry on asking questions.

Kit