Seeing that I just ordered new wheels today, I'll bite. Whose tires are you having this much success with?
My preferred tire brand is Continental. for both Tandem and single bikes. For the Tandem we've run 700x25 Continental GP4000 but currently we're runninng 700X28 Grand Prix 4 Seasons becuase the GP4000 do not come in 28mm width.
The other brand that is well reviewed here and elsewhere is Schwalbe.