Wow, I 'm jealous. Up here in Massachusetts the stores don't sell individual canna rhizomes. I think it's great you get to rummage through and pick the best. I would think you can plant them now. Cannas should be winter hardy in zone 8. What kind are you buying?

I would just keep em stored for the winter, plant em in spring. Great deal ya found there!

I found nice deals on Ebay. Here in Paradise (Florida) we do not dig up our rhizomes and store them. I have 11 cannas all potted in large pots on iron stands I found at Home Depot. I bought orange punch canna on Ebay, and a giant red type from a person in Australia. Many canna growers around the country are happy to sell premium rhizomes cheaply on Ebay. Search for canna rhizomes.

I've found good deals on canna seeds on ebay, but the rhizomes seem a little pricey, especially when you add the shipping. I would think the best deal price wise is Lowes or HD.