Received NG pool spa heater quote, did not like equipment recommended.

[Restomod]

Currently have a Natural gas 400K Hayward Pool and spa heater that is 20yrs old and is giving me maintenance required errors. I'm looking to replace the heater for the spa only as we never heat the pool in Texas. Received a quote for a Jandy JXI for $6K installed but have read there are valve issues that are often problematic. We would never heat the pool, just the spa which is a spillover waterfall type.
What heater would you suggest for cost and reliability/longevity?

 

[PoolGate]

Valve issues? There are no valves in the jxi and generally it's a very reliable heater. $6k is astronomical. Can't you do this work yourself? Replacing a gas heater with a gas heater isn't hard.

How big is your spa? You could probably get away with a smaller one like 200k but it'll just take longer to heat.

 

[ajw22]

Post pics of your equipment pad and the Hayward heater.