I love the DW topper and may get the Dalek head motor kit if I could find at a reasonable price. The topper lights up in unison when the Dalek talks as you progress throughout the game. The kit makes the head turn as well, which was the original inent before cost cutting moves.
Other factory toppers are a must IMO. Without it the pin is incomplete and when they interact the really add to the game.
The OP may really be talking about after market. They look nice is the reason