Personally I would reduce the pressure coming into the house.
The reasons are as follows.
1- Excessive pressure causes excessive velocity and thus possible erosion and NOISE
2- The excessive pressure can destroy piping because of hydraulic shock from quick closing valves like solenoids dish washers and washing machines.
3- Isolating a pressure vessel from a system is always a bad thing to do in case of a run away firing condition.
4- Expansion tanks are NOT normally required on a hot water heater properly piped in with the right supply pressure
All you need is enough pressure to over come friction losses and then some to have the required pressure to activate the fixture properly.
To find the pressure you really need take the incoming pressure you have and times it by 2.31 this will tell you how high this water will be elevated.
I never let any more then 85 PSI into any structure and this will elevate water to a height of 196 ft
Figuring if you needed even 25 PSI on the upper most floor for a fixture to operate at its peek demand all you do is take 25 times and convert it to feet by using the following formula
25 2.31 = 57.75 ft then take the height of the highest fixture from the water main and times that by . 433 to give you a footage reading
Here look at this 57.75 ft. Is how height 25 PSI will take you.
to prove take this 57.75 and times it by . 433 = 25.00
EVEN adding another 10 PSI for friction losses etc. you only need 35 PSI incoming pressure so give it a fudge factor of 20 PSI your still at 55 PSI INCOMING and yet your should be well under the CDA (copper development associations) recommendations of 8 FPS Velocity
A pressure of 55 PSI would give you a velocity exceeding 25 FPS and flowing through a 1″ pipe your flow rate would be 62.5 GPM THINK about it?
Today with the low flow shower heads and faucets where are you actually going to get this kind of flow conditions other then possibly an outside hydrant.
Most journeymen plumbers today think like car mechanics wanting to get SPEED through piping systems as they love the roar of water shooting past washers and the loud sounds of hydraulic shock (water hammering)
What good is having a car with 300 HP in a 35 mile an hour zone?
Do you think you really need water pressure coming into your home that can reach the moon?
Think of the results when your washing machine hoses give up the ghost ad here you have a zillion pounds of pressure WHY?
Just have a Licensed Master Plumber come over and Properly size the pressure required for YOUR home.
DO NOT let a NON licensed Master do it as most journeymen cant be bothered with facts as one size fits all.
I know I have “journeymen” working under my license and NO WAY would I trust them to properly size a piping system for peek efficiency.