Romance is one thing, marriage is quite another.

爱情是一回事，婚姻却是另一回事。

That's quite another matter.

那完全是另一回事。

Listening to music at home is one thing, going to hear it being performed live is quite another.

在家里听音乐是一回事，去到现场听又是另一回事。

Of course if you were Badger or Otter, it would be quite another matter.

当然，如果你是班杰或奥特，那就另当别论了。

That's quite another thing.

那完全是另外一回事。