you're so full of it man... i don't put my all into working out, in fact, i do one leg workout per week. despite this, genetics have allowed me to squat 600 at 195. the only difference is that i'm 5'9". i have a friend who's 6'3" who uses around 400 lbs when he squats, thinks he goes to parallel and comes back up. in reality, he goes down to maybe 115 degrees. i'm not going to call you outright weak, but before you make your claims, make sure you know for a fact that you're going parallel. just because your friends say you are, doesn't mean you are.
and as far as you being able to get your squat up to 600... man, if your claims are true, i'll give you a little over 500 for max. now, do you really expect it to be "easy" to add another 100 lbs to your squat??