Before you change the equipment in a complex system like a geothermal heat pump system, you should understand how the system works and why each part was selected, and the performance characteristics of each part. An important part of owning such a system is to understand it or be willing to pay someone you trust to understand it for you and make recommendations to you that aren't affected by what they want to sell to you.
For example, do you have a diagram and operating description of the system? Do you know the flow rates in the system and the characteristics of the pumps? Do you know the capacity of the heat pump system?
Some geothermal heat pump systems use a pump to bring in the water from a well and reinject it to the aquifer. Others have a buried heat exchanger with a circulator, and the only head loss is in the pipes and heat exchangers. If you have to waste the head in a control valve, you are wasting some power, which may be necessary if the water table is very deep or you don't have a means of recovering the pressure energy. If it is a system with an underground heat exchanger, you will have completely different pumping requirements than if you are pumping water from a aquifer.
If you are replacing a pump or the whole system, you should start with finding out the design characteristics of the pump and other parts of the system. Unless you understand the engineering principles and characteristics of the system, you shouldn't change any part of it.