First off that is NOT a golf cart and your wife is one lucky woman.
I think the reason you see so many Polaris Rangers on the resale list is because of the off road craze. I have a Yamaha Rhino for the desert the main competition is the Polaris Ranger and Razor. The Ranger has a high center of gravity so it is not the ideal off road toy. I think this is why the Razor was developed. Low and fast.
The Rhino and others usually have something called a aftermarket CDI added to make them go faster. I have one but I have no idea what CDI stands for. It's a tiny box adjacent to the battery. Maybe they have something like this for your Kubota.
I am jealous of that cab. The heater sounds great. No freezing wind blowing in your face..... Ahhhh!!!!!