Yup. the floor to celling cabinet is an issue.
Even if you use LEDs, you may also face the same issue cause of the ventilation problem.
Maybe try contact Razali and see if he has any tips. (aka Dr Evil - DELightings.)
He might be able to help/ advise.
Chiller.... think you really need to change one and place it outside.
or change to a smaller sump. a lot of work