It is a wonderful list. Ordering one or two from several companies does make the shipping cost something to keep in mind.
Sharon - while I don't have recommendations for the humidity situation, I would say to keep them well spaced so mildew doesn't attack them. It does get to some of mine during October. They do want air circulation and I failed with that since the three Peaches 'n Cream grew to 6' tall and ended up very wide, which blocked a lot of the breeze they needed.
Favorites: (alpha order)
Accent Dahlias - Ken Greenway. Nice video here:
http://www.youtube.com/watch?v... This is his site but next week he will have his 2014 site up and running.
http://www.dahliasuppliers.com... He is just as nice on the phone as he is on the video.
Corralitos Dahlias (not Corralito's) Kevin Larkin is a very nice guy, too!
http://cgdahlias.com/index.htm...
Dan's Dahlias - the site:
http://shop.dansdahlias.com/ Dan is the owner. Very nice video here:
http://www.youtube.com/watch?v...
Hollyhill Dahlias - already has sold out some varieties but the site is open and ready for ordering! Ready, set, go!
http://www.hollyhilldahlias.co...
Swan Island Dahlias - very highly regarded!!!
http://www.dahlias.com/viewall...
Very good video on digging and dividing dahlias. Even if you don't live in an area where the earth freezes, watch this video to see how to dig and divide or you may find, as I did, dahlias can get so huge they are starved for food and they can die a slow death.
http://www.youtube.com/watch?v... Some dahlias provide a lot of tubers with eyes and some will only give you very few - that's normal.
There are so many more dahlia vendors. My personal preference is to buy from only dahlia vendors and not online sites that sell a multitude of plants but...I have a great dahlia friend who has had fabulous luck with even (sigh) Michigan Bulb Company.
Also, don't disregard Home Depot, Lowe's, or Walmart. In early March, here in NY, they have the full assortment so don't dismiss them. If you watch the video about digging/dividing and feel it might be more work than you want (especially in nasty cold, dank weather) you just might decide not to dig and just buy a few bags of them at $6.98 or $9.98 - well worth it. Each bag can have 3 to 4 dahlias.
You can pot them up in ONLY slightly dampened medium and put them in a sunny window. DO NOT water again until you see growth and then only lightly. More tubers will die from too much water than not enough.
Sharon - it would be worth it to you to call the vendor of your choice (maybe one in your zone or in your area) since they'd be more acquainted with your heat and humidity.