I don't think I'd go with 55psi. I've had both 25psi and 40psi ParMax 4's on board for the past seven years.
They are not super-long lived (but then again, they get ~lots~ of hours on them) and they don't like continuous duty (definitely not for 15 minutes straight).
Having said that, I can certainly recommend them because they are widely available, relatively inexpensive and a breeze to swap out with those snap fittings.
The 25psi experienced some notable flow rate drop when using more than one day faucet, but the 40psi model remains pretty steady in the shower with the washing machine going and another tap in use.
former owner and still Loving it :)