So many other factors go into an engine like capacity to move air efficiently that I feel comparing # of cylinders to displacement is not really fair. Other factors aside I'd want a good balance, thats why small block V8s are so popular, good useable power, decent rev range, and they just sound good.
Maybe you should consider the strength of the engine with as little mass as possible, then get it to operate over 100% volumetric efficency, then you can see how much displacement you can get into that formula. Thats whats the best. Hows that for a lame attempt at sounding smart?