KFG: The old pond a little over 4500 gallons. Definitely low-tech, labor intensive to maintain, only 4' deep at the deepest spot and poorly configured/shaped. Due to site limitations, personal foibles (garden issues & aesthetics), and zoning requirements, the new pond will not be my "ideal" pond. But, even I draw the line at razing the house to make the pond fit better.
Tony: Since I am doing virtually nothing myself, the cost is in the same range as using gunite. In many ways gunite allows more flexibility. In my situation, however, the extra time involved and the lack of contractors truly knowledgeable of koi pond design makes this approach work much better ... if it works!