It must be very exciting as you pull the dahlias out of storage. 279 tubers is still a LOT of tubers so I salute you in digging, splitting, and storing so many.
How in the world did you manage with 300 varieties (assuming you have multiples of some so the actual number of tubers must be a lot higher). And all those pots.....you have a lot more energy than I.
I also told myself no more additional new tubers this year. The 5 that I split, I gave the extras away. I only have about 65 dahlia plants total, maybe 50 varieties. I don't have much of a back yard, so have to intersperse my dahlias in the front yard. Since I leave most of them in the ground, I only know if they survive the winter as they sprout out - I lose more dahlias to snails than not having the tubers survive the winter. I was also trying to cut down on the amount of work in the garden......
I grew my first dahlia 6 years ago - getting maybe 10-12 new ones a year. It was hard resisting the temptation to get new ones. As I look at what other people are planting, I am beginning to regret my decision in not getting any new ones this year. There are so many neat varieties out there.