I agree with GiantSlayer... it's really not about how heavy you can go. I use two plates, sometimes 3 per side but no more than 3. I also like the security of a smith machine while performing my squats. I don't work with a partner so safety is an issue with me. But if you get 12 good deep squats with 2 plates a side for 4 sets should make your legs not only strong but bigger. I've never had problems with my legs, I love 45 degree press machine also. Now there I can stack on the plates. You want to burn your hind end do 45 degree seated presses. Also I love the Hack but like my squates I don't exceed 2 plates a side. Something else you may want to try is straight legged deads. You don't need a lot of weight, the bar and a few dimes will do the trick, but that burns the hell out of your hams.