Take this with like a truck full of salt; I looked into reopening my extraction spaces and still can't decide what to do.
It may indeed be the best thing ever for a lot of people both from an aesthetic perspective AND a functional perspective, but it is also potentially ripe with problems. I'm under the impression that moving teeth that much, to reopen the extraction spaces, is tremendously hard on both our teeth and gums (root resorption, gum recession, etc.). Another thing to consider is the life of the implants. They essentially come in two separate parts: the root (implant), and the crown (visible part of the tooth). For the implant (root) two materials are available: titanium (common), and ceramic (newer and less common). (If I go this route, I will pick ceramic. I personally believe it to be superior, but that's certainly debatable.) So you'll have two separate parts to maintain for the rest of your life! Most people seem to do really well with implants, but keep in mind they can fail at any time (become loose, fall out, etc.), and they don't last forever, either. I was told between 8 and 25 years is the life of an implant if everything goes perfectly. Also, crowns don't last forever (I was told 8 years is standard). Another thing to keep in mind, and someone at the office should have told you this, is that you can go through this entire process and still end up needing surgery. I looked into working with Dr. Hang, and the one thing I really appreciated about him is that he acknowledged right off the bat that many of his patients still end up needing surgery to create an optimal result. I didn't read the entire thread; I'm not sure of your specific circumstances, so I don't know if that applies to you.
I think if all goes right this could be the most amazing treatment ever, but I just personally see the potential for SOOOO much to go wrong. It's a tough call.
The $20,000 you were quoted sounds a little high, but maybe that includes the splints to stabilize your joints, too. If it includes that splints/appliances/whatever that price is probably about right.