Use a plug-in test light and determine what else is on that circuit.
If you're doing a remodel, you'd just as well get all of your small appliance circuits GFI protected, if they aren't already. If the receptacle under your counter is already protected and isn't a fully loaded circuit, you can use it. Switch it anywhere you want but installing it close to the source would simplify things. Most kitchen circuits are 20 amp circuits so you will need to use #12 wire. Keep your wiring protected and out of the way. A screw through a wire can cause a whole mess of trouble