Hi,
I have had both of the hedychiums that you mentioned. The gardenium didn't have time to develop in my zone. It reallly needs tropical weather.
The coronarium does well and smells DIVINE!!!! I think it's tougher than the gardenium. So, give it a try.
AT

I'm Zone 8 and I'm still waiting to see if any of my
Hedychiums have survived the winter, so far no sign of
life but I do know others in Zone 8 who have been
growing them in the ground without any problem.

My Peruvian Daffodil 'Sulphur Queen' is more fragrant
than my white one x festalis but I have
read that there are some extremely fragrant white
ones as well.

I grow several hedychiums, both in the garden and the greenhouse, and I must say my Elizabeth and Thai Spirit are my most fragrant....Usually, My Luna Moth and coronarium are very decent fragrant plants, usually toward the evening time.....