Steam cauliflower until just fork-tender. (Don't overdo it, or it will become mush later.)

Meanwhile, cream together the cream cheese, cream/milk, and 1-1/2 cups each of the cheddar and mozzarella.

Season to taste with garlic powder, salt, and pepper. (Keep in mind that you're essentially salting the cauliflower, too, so don't go too light.)

Drain the cauliflower if/as necessary, then mix into the cheese mixture.

Spread cauliflower/cheese mixture in a greased 9x13 baking dish.

Sprinkle with remaining 1/2 cup each of cheddar and monterey jack.

Cover and bake at 350 for 25 minutes, then remove the cover and continue baking until cheese is bubbly and beginning to brown.