You would do well to avoid Horn. Read my post below regarding virused canna.

Karchesky and Harris are pricey, but you get what you pay for with lack of disease.

Have your local nursery order from San Marcos. They will only sell non-diseased rhizomes also.

Look for local plantings that are virus free and ask for rhizomes (free) or perhaps to buy on the cheap.

Gardeners are generally friendly and accomodating people.