Ugh! Refrigerators- the bane of kitchen designers. Ranges and ovens come in nominal sizes and dishwashers are all the same size, but refrigerators are all over the place! Back when I sold/designed kitchens, one of the first questions I would ask is "What appliances will you be using?" Was not uncommon to hear "We want to use our existing fridge." "How old is it?" "Only ___ years." "Fine- we don't sell appliances, so happy to include whatever you provide, but I still want you to shop for a new refrigerator just as if you had to replace it tomorrow. That way, I can design the space for both using filler pieces as needed."

Don't make the mistake of insisting on something to fit all your criteria. For instance, you may have to settle for the dispenser setup to get a good unit. Better to work within the offerings of a dealer who provides good service than be stuck with a unit you hate just because 'Well, it fit the hole...'