Question about my car?

I have a 2004 M12 GTO. All it has done to it is exhaust with x-pipe, Cold air intake, programmer, underdrive pulleys, and 100 shot of Nitrous. Well I'm wanting to put a cam in it now. I was thinking a 218/224. Do you think I can get away with putting it in with only hardened push rods, or would I have to put in valve springs as well. I heard that if you don't race a lot or go to the track, you really don't need to change the valve springs. And I really don't race a lot at all. Maybe once a month. I just like to have to power there just in case someone wants to be a dick on the highway and mess with me. So what do you guy's think? Will that be okay? or should I get a smaller cam or could I get an even bigger one? Thanks a lot. And also.. Anyone that really owns a GTO knows that they sorta lack on the low end torque side. Will a Cam help with the low end torque?