I agree with you that Asteroids is one of the best home ports of the game. As for the POKEY, they couldn't fit it into the board because they wanted to maintain the 2600 compatibility. Their plan was to add it to carts and GCC had even planned to make a chip as good as the POKEY (if not better) that would be cheaper than the POKEY. That would have made it practical to add it to all the carts. Unfortunately, this was when the Tramiels bought Atari and they scrapped the whole thing.