jcummins,
To be honest I can't imagine needing more light than what these put out. There are no dead spots in the beam pattern. They over the power the stock headlights 10 to 1. In fact it's very difficult to tell when the stock headlights are turned on if the LEDs are already on. Given the limited top speed of the 855D I'm not certain you'll need anything more powerful. People that have used my gator at night can't believe the difference over stock. Then again I mostly use the gator in the woods and around the house.
They are cheap enough not to give them a try. If they don't meet your needs mount them in the rear or use them as supplemental reverse lights on a pickup/SUV.
How far does the window stick up into the poly roof? I've never seen a gator with windshield and poly roof 1st hand.