Like I wrote in another thread, I have tried many of the commercial sounds available for the Tyros 2 and in my opinion they are not even close to the quality of the internal samples. So my advice to potential buyers would be to buy just the sounds that fill a gap in the Tyros 2 internal wave set, like choirs and vocal samples. On the other hand, there is really no point in buying samples of woodwinds or guitars (for example), because there is really no comparison with the T2 own sounds.
Speaking then of the Tyros 3, from what I have read it is still lacking in the same areas as the Tyros 2 (especially choirs and vocal sounds), so the advice to buy external samples is still valid (unless you can sample or import your own, which I think is the best and also the cheapest option possibile).
Finally, speaking of drums, no manufacturer that I am aware of offers drum sets for sale for the Tyros.