In a large baking pan or cast iron pan place a layer of the tortilla chips and cover with the shredded Cheddar and Pepper Jack cheeses. Bake the chips for 2 to 3 minutes, or until the cheeses are melted. Remove the dish from the oven and set aside.
In a large saute pan over medium-high heat, melt the butter and saute the garlic until soft. Add the crabmeat, shrimp, and scallops and saute for 3 minutes.
Add the cream, garlic powder, Parmesan, salt and pepper, to taste, to the seafood and stir for 2 to 3 minutes, until the sauce has thickened.
Remove the seafood mixture from the heat and pour over the tortilla chips. Top the nachos with shredded lettuce, pico de gallo, jalapenos, and a large dollop of sour cream. Serve immediately.