I'll disagree with this. I blew my legs up with just the leg press and machines when I wasn't able to squat. Sure, squats are best but you can still be quadzilla without them.
@Nitrust have you tried an inversion table for your sciatica? I assume you already do loads of core work
No I have not tried and inversion table. I don't know of anyone that has one and my gym definately dosent. I am staying away from any exercise that causes me pain. I cannot hurt all day, it's exhausting at work, especially when it's 100 degrees out and being in pain sucks even more.