I am not a huge fan of smith machines. They do not allow your joints to move through their natural plain of movement, and when used with heavy weights, the wrist rotation on release and locking of the bar can cause problems. Also because they are a machine, they remove the core engagement of true free weight exercise.
Squat, or deadlift on a smith machine and you will more than likely injure yourself, plain and simple.
Now a power rack with an olympic bar
oh boy, having one of those at home is a dream come true. The single greatest exercise tool since the barbell was invented.
Thats money well spent.