Unfortunately, insulation and sound proofing is not required per code between conditioned spaces in this case.

It is also worthy of note that additional insulation between the floor will do very little to impact the noise tranmission as a majority is carried via vibrations on the framing. 

There are applications and techiques that can can be deployed.  All of them will require removal of the existing ceiling if you stay with a drywall finish.  You can run resilient channel in addition to sound de-coupling isolators. 

It is not an easy or cheap bullet fix in this case. 

For those items that you mention there, it would be cost prohibitive to replace the entire unit. Keep in mind, most of the newer toilets do not include the best seats either.

Chains are easy to swap out as are the seats.

Happy DIY'ing.

John,

Where is the home located in terms of climate region. There are some nuances when it comes to tuning glazing packages per elevation.

Keep in mind that standard Low-e glass will reduce the amount of radiant energy that enters through the window by more than 200% over clear glass right off the bat.

WoW Home Solutions