My Aquatherm Air Handler System Internal Evaporator Coil has a leak. Just replaced the coil 2 years ago. The system is about 10 years old. Should I replace the system with a Heat Pump or simply use AC Smart Seal? Note: The Aquatherm by The First Company has a reputation for inferior coils that often have pin holes. Estimated cost to replace coil $2,500. Estimated cost to replace the entire system $15,000.