This is an old post, but a relevant question!
I work on renovations in the city in addition to being an agent, and we always do our best to match brands when renovating homes, but since this is your new home (congratulations by the way!) I'd say it's all a matter of preference. Both KitchenAid and Viking are great brands - I personally prefer Viking as do many buyers, but both are good, so if you wanted to match your new appliances to one of them that would certainly work. You could also look at the handles of your range and ovens and see if you can find something similar to that in your fridge, as that will make them look matching, even if they are from different companies. If the ovens and ranges have different handle styles, you might want to try finding something that coordinates with both to bring all of the appliances together. In any case I'd suggest sticking with the same color scheme if possible (i.e.: black, white, stainless, or custom cabinet).