You have got to make up your mind if it is a engine/horsepower problem or a transmission problem - hard for us to tell from the description.

Transmission complaints on the Automatic Crossfire are really kinda rare ('cept for the fluid leak thing that everyone seems to get). I don't' follow such threads, as my current car is a manual (as ALL Roadsters SHOULD BE!)

But, anyway:
How many miles on the car?
How many miles since the service was done on the transmission?
Did it start right after the service, or, say, 10,000 miles after? (Thinking bad/wrong fluid or wrong quantity of fluid here, should have shown up really quickly.)

As to the engine:
Do you have any starting problems?
Rough idle?
Stalling?
Any of these would add to the evidence your transmission may not be the problem.