I know the Costus pictus is a solid Zone 8 hardy .. at least for me - doesn't bloom every year though. I have another Spiral ginger, Cheilocostus speciosus 'Foster Variegated' which is suppose to also be Zone 8 hardy but I got it about 16 months ago as a rooted cutting (had no idea you could root ginger cuttings) and I've been keeping it in a pot .. it actually started making rhizomes this year so I'll probably be putting it in the ground next year.
An interesting thing about that rooted Costus .. the leaves/stems for the first year I had it were totally deformed - no spiral and crinkled up leaves .. I was about to write it off this Spring when new growth started coming up normal! I'm thinking that the growth of the rhizomes instead of just roots finally straightened it out so to speak.
