Do you need an AD / DA? No, you already have them.
There is an AD on the input of the VS800. There is a DA on the output of the VS800. Your sound passes an AD in the VS880. There is a DA on the output of the VS880. There is an AD in the CD burner.
So your chain already has three AD-s and 2 DA-s.
Do you need a better converter? Only you can be the judge. There are "better" stuff than the 5 your chain has. It is your ears thought that should be pleased and you wallet that has to pay for it.