one thing you may want to consider is a counter-depth refrigerator unless your heart is set on a true built-in. by using a counter-depth refrigerator, you can avoid the need to alter the existing cabinets. for a few hundred dollars, you can probably have a contractor (or less if you do it yourself) add matching cabinet pieces to fill in the gaps around the counter-depth refrigerator to give a similar look to a true built-in... and save yourself ~$5,000.
we chose a kitchen-aid counter-depth and had a contractor fill in the space and spent a total of ~$2,750. if we went with a true built-in by kitchen-aid, the total cost would have been ~$8,000.
the end result for us was that we kept the overhead cabinets (which would need to be removed if a built-in was added).