3S with 1900kV motor should lower temps if gearing is kept the same.
However 1900kV is likely too low and you'll see reduced top speed, as the rc guy says 2200kV on 3S will maintain your current top speed. You can calculate this yourself, as motor kV multiplied by voltage will give maximum RPM attainable by the motor. In this case 2200kV with 3S (11.1V nominal) will give a close performance match to your current setup if gearing is kept the same. It shouldn't really be much harder on your driveshafts if the parts you choose aren't much heavier, maybe a little.

Just make sure physical fit is OK and your replacement motor fits your mount and you can get an appropriate pitch and ID pinion.
Motors that low in kV are often larger (for 1/8 scale) and use 5mm ID pinions. There may be limited choice in low kV motors matching your setup.