I think the '03 Dyna was still a carb glens.
Supershooter, I can't imagine you would notice much difference at all if all you replaced was the coils. Harley offered coil and ignition module combination kits through the SE catalog that altered ignition advance curves to match up better with other modifications, and also offered one that was programmable so you could change the curves yourself. If you have mods that would benefit from ignition timing changes, then yes those can be useful. But just a higher output coil isn't necessarily going to do anything if you're not experiencing spark problems with the current coils. A higher output coil will fire a worn plug or wider gap better, but if you maintain your plugs properly it isn't needed on a relatively stock engine.
Jerry