Don't forget C5 Ignitions, too!
I have run Dyna S and Dyna 2000 with 5 ohm and 3ohm coils. On a 550, the 3 ohm coils can tax your battery. Some people have had issues with Dyna 2000 reliability (for a certain production time).
On my newest build (650 engine in a 550), I decided to pop for the C5. It will allow me to ditch the CDI boxes (known weak link on the 650) and the technology with the C5 is impressive. We'll see how it works out!