John;
You might want to read through
this thread about the MSD. I doubt that you will find any HP that will show up on a dyno. In that regards, if the current ignition is "good enough", then putting a stronger/faster/longer ignition system won't get you much since anything more then "good enough" is still just "good enough".
I can say that where the MSD will help is to clean up the running below 3000 RPM. This may not be an issue on your 2.4 because it has an improved combustion chamber design over my 2.0 with S pistons. But with my car, the MSD did cure all the popping and mis-fires that which plagued my car at low rev's as a result of the very compromised combustion chamber design. It also cured the plug fouling problem it had as a result of the aforementioned misfires.
So if you car is having similar issues, go ahead, get the MSD. If it's not, then you may want to use the money elsewhere.