Be patient with the slow tubers. Put them somewhere warm planted in slightly moist loose potting mix if you want to encourage them to start sprouting now. Are you planning on propagating them from sprout cuttings? This isn't really a task for a beginner but if you want to try there is good info on the web.

http://www.dahlias.net/dahwebpg/Propagation/Cuttings.htm

http://www.dahlia.org/index.php?page=success-with-cuttings

Thanks Steve.
Yes planning for propagating, will give it a try on some tuber. For rest, I heard that only one sprout should be there when we transplant and should cut rest sprout, is that true?

Will check those links.