Hey Chris, EE's - black stem/fontanesii, chicago harlequin, portadora, illustris have all wintered fine for me even without mulch. Black Magic has yet to survive our 7a winter even with a heavy mulch. However you're a 1/2 a zone warmer than me so BM may do fine for you. Colocasia in most cases (but not all) tend to be hardier than Alocasia. They can handle the cold just not the 'wet' cold.

The only banana I've wintered in the ground has been the chinese/lotus bloom and it is super hardy. This will be my first year trying basjoo in ground but from what I've read it should do fine. I will have backups just in case. Those will be stored under the house or in an unheated detached building. The Basjoos have done fine there previous winters and so did the cuculatta EE.

If you go to the main Carolina 'Discussion' board and do a search on both elephant ears and bananas you should find some good discussions on which EE's and Bananas do well and how some people winter them.