Tire brand can make a huge difference... The previous owner of my SRT had installed Nittos on the front... very harsh. I had Continental DWS on my Mandrus wheels... even with the tires being shot, the ride improved

So, tires are certainly a contributing factor. If your car has a decent amount of miles on it, a good set of shocks would work wonders as bad shocks will ruin the ride quality. Bilstein shocks are among the best if you're at stock ride height... $400 for a set and they're a breeze to swap out.

Aside from that, the Crossfire is simply a firm-riding car. If you think the Limited is bad, you should drive an SRT-6. The suspension in that car is as comfortable as falling down a staircase.