okay, i'm just saying that using the term "box squat" is going to confuse people ("people" meaning "me" in this case, haha). i tend to do them with a bench as well because we have some hilariously strong ones and i can use 5 plates without the thing even bending.
i said front squats not because they're even remotely similar to a box squat, sorry if it seemed that way. what i was saying was that if the question is "what depth should i go to in order to hit my quads the best", it might be a good idea just to front squat and not have to worry about if you're doing it for maximum quad activation or whatever.
i'm horrible at them, largely because i don't do them and partly because my squat training for the past few years has left my quads pretty behind the times while my posterior chain started to take over. but i think they're fantastic for the thighs, especially if you have a shoe with a heel (or alternately a flat shoe with a 2.5 plate under your heels).