What Curtis said.
Just my experience, but if you enclose it, you might not need a heater. I have the teryx 4 and am super happy with it. I built my own enclosure and find that it is plenty warm in the winter. I have only had it out in the high 20s low 30s, but it was good enough for my wife. it was not HOT inside, but it was "comfortable". Once the engine heats up of course.
and I am a BIG fan of a glass windshield