Soundproofing between floors

we're doing some reno's to a property where the kids bedrooms are upstairs and family room and master bdr downstairs. we'll be getting new carpet for upstairs floors but wanted to do something extra to stop TV noise going upstairs and teenage girls music going downstairs.
i've asked lots of builders & carpet people and have got a different response everytime.
these are our options so far:
- lay marine ply or similar on top of current wooden floor - + normal underlay & carpet.
- use an acoustic underlay, + carpet (more than $35 sq m)
- use both of above (but very exp)

My alternative is to lay a very good commercial underlay like Dunlop Ultralay (but don't know cost), has higher density than residential stuff.

(ps. there's no possibility of installing insulation between floors)

Any advice will be very gratefully received - I really don't know which way to go


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