Did you know there is a simple exercise you can do at home and that can build MASSIVE quads? It requires no machine, no special equipment, and little to no additional weight. I would argue sissy squats are better for overall quad hypertrophy than regular squats, as sissy squats heavily stress all four heads of the quadriceps (unlike regular squats which can't stress the rectus femoris head that much). I haven't done a "proper" barbell squat in many years now, as I don't have enough weight for that in my home gym, but as you can see at the end of the clip, my quads are doing well. Be warned, though: high-rep sissy squats BURN. A lot.