Wings and spoilers function differently but the end result is the same. First a little background.

The shape of the Crossfire mimics a wing and as a result lift is generated. In order to have lift you must first have a high pressure zone and a low pressure zone. Obviously in the case of the Crossfire the high pressure zone is under the car and the low zone is above. Both zones are pushing against the car but the high pressure zone pushes with more force and lifts the car. The low pressure zone is not strong enough to counteract the high pressure one to push the car back onto the road. So how are these zones created? It's done by air being moved faster over the top of the car than the bottom. Look at the Crossfire in profile and mentally draw a line from the grill, along the hood, over the top and down the back. Now do the same except go underneath the car. Which line is longer? Since air molecules like to "hang together" those that go over the top of the car must move faster (since they have a greater distance to travel compared to those going under the car) so they can meet up with their respective drinking buddy molecules at the rear of the car. This accelerated mass of air has less "push" against the car compared to the air underneath. Another way of looking at it (and maybe easier to visualize) is that you have the same number of air molecules above and below the Crossfire. Since the molecules above have a greater area to cover (remember our mental line) they are spread out more and have less weight or push per square meter, foot or whatever the measurement of your choice.

What a spoiler does is to disrupt or kill the airflow over the top of the wing or Crossfire in our case. No airflow means that no low pressure zone is created.

Now I know that many members here already understand all of the above but I thought that those members not as knowledgable about aerodynamics would appreciate a basic primer.

How Chrysler determined the amount of downward force generated by the spoiler is beyond me. Part of the problem may be that it actually is a wing and is just misnamed. But from what I've seen of it I would call it a spoiler.

The gizmo on the back of the SRT-6 is a wing. It is shaped like a wing and is designed to allow air to flow over and under it.

Now for another basic primer on the SRT-6 wing. Imagine the Crossfire in profile in all it's lift producing glory. Now iimagine another profiled Crossfire except this one is little. Flip the little Crossfire over and stick it on the back of the big Crossfire. There's your wing. Just as air is pushing at the bottom of the big Crossfire, it also pushes at the bottom of the little Crossfire. And the push of the little Crossfire is what keeps the rear of the big one planted.

And why a wing on a SRT-6 and not a spoiler? I'll echo the thoughts of others that it is more effective for higher speeds and acceleration, and that it makes the SRT-6 standout more from the standard Crossfire. But I'll add that I think Chrysler went with it to keep costs down.