I have new oak kitchen cabinets that I would like to put an additonal coat of clear finish.
Can I use urethane and if so - water based or oil based?? If not urethane, what can I use?

I'm remodeling the kitchen and using natural maple cabinets. They are made of maple wood, have no stain, but just a urethane finish. Very light color, but popular. Would black or white appliances look better with these cabinets? I'm selling the house, so I don't want to buy expensive (stainless steel) appliances.