I would expect a quote to include a detailed review of which walls will need to be knocked down? I know when I had a plumbing quote down they walked me through the house, pointed out what needed fixing, what they would have to tear down to get to the pipes...the whole deal as a way to justify the quote. I would ask them for the same thing...why are they saying $6000 or $10,000...what is the expensive part (time?, new electrical panel?, pulling wiring?, etc....get details then you can see where the difference in the quotes come from and make a decision based on that...not just a number)