I've been running the novak gtb/4.5 for a couple of months now. heaps of power, very driveable, 100% reliable to date, no maintenance. I can't imagine going back to brushed motors. I've run on small, medium and large tracks and had competitive horsepower. Run time is now no issue.
I've personally not had the unit thermal or had any fan related issues - but the Much More fan is a straight bolt on replacement to move a higher volume of air if required.
Go for it.