2006 Chevy Monte Carlo Pulse

When I bought this car in 11/08, it had a serious wobble in the front end. Especially when I applied the brakes.
Based on proffessional mechanics recommendations, I have replaced the front rotors, pads (new ones are ceramic), wheel bearings and inner and outer tie rod ends. The wobble disappeared for a few months after I replaced the rotors and wheel bearings, but now it's back and it's only when I apply the brakes forcefully. I don't think the rotors are warping already, in fact, it feels more like something in the drivetrain or steering column.
Anyone know where to go from here or what to check?
Thanks,
Bob