First off always take your time and listen to your body.
RampantBadger and hypem74 both bring up good points;
Do you have a program you are doing?
Knees past/not past toes?
I would suggest looking at a program as it may really help you out. Also in regards to front squats.. If you are looking to really hit the quads, front squats (in my opinion) are king. There are VERY many different variations of front squats too, so look them up.
I would also suggest lastly, if you are going to experiment with different exercise just take your time and remember how you feel. If you really want to target muscles, slow down. Strength is explosion. Hypertrophy is time-under-tension.
When I work out legs M,W,F for what I do, I do my weights slow. Slow drop in squat, slow raise.