ProStick + , external amp + filter combination?

It depends. You have to see the NF at the frequency you plan to use it. But yes, SPF5189Z is very good, a GaAs pHEMT that was impossible to get a few years ago.
I don’t know what mine has, the guy tried to erase it, maybe someone else has better eyes:


PS: Those are taken with my Samsung Galaxy S7 Edge and an LED flash light.