Yea, I agree, no doubt Squats are the best for overall mass for your quads.
Leg press & squats work upper to mid quads mostly, while leg extensions develope more of the lower heads on your quads.
BTW: it's called called quads because of the front leg muscles above the knee contain 4 main muscle bellies.
Leg ext:
Just make sure you work your legs out for each head in proportion to how you want them developed. Another words you wouldn't want to just do upper quad excersises and leave out lower quad deveopment, or hamstrings (which give that curved strong look to legs.)
Hamstring excersises that work nicely are deadlifts (mostly for mass), hamstring curls (mainly for isolation and shape/development)
Hit your calves as well, it's way too common for people to have chicken sized calves that don't match thier upper legs.