Can you clarify if this is a new pool or existing, if existing are you able to advise what is in place currently, as this would normally be spec'd as part of the pool design.
In order to identify a suitable heater I need some additional information:
What do you want the running\idle temp to be 28, 30, 32 degrees?
The flow\turn over rate of the pump
Is this an indoor or outdoor pool
Is this just for pool water or ambient heating as well
What is your preferred heat source, gas, oil or electric?
Are you wanting this to integrate with an existing heating solution