A 4" cement slab would have been better. Also, I have problems with sand as when it settles down, sometimes it does not level properly that your slab flooring can be misaligned. Also, if the sand is not well dried up, you can have all sorts of "insects" and "maggots" growing in it. I have a client whose home theater was floated using that technique and "bukbok" thrived in the sand. They had to renovate the entire home theater, installed new flooring, fixed the walls, etc. but there is a stench smell, that until now, they cannot seem to eradicate. The better way of floating a floor is to use neoprene pads placed properly, computed in such a way that it would have a real low resonance factor. There is a formula for that and it is available in any acoustic or noise and vibration book.
Now, would you need the pads to float your flooring using neoprene and all? If you are able to achieve your desired result, let it be. You've already spent lots of money. You just have to watch out on things that might grow underneath your flooring.
FWIW