Protection will be the first you want to do. Skids (get full belly, sides, front and rear), rear brace, cv guards (if you want), and anything else you might have to have to protect the RZR from the obsicles you will face in your type of riding. 2nd, I would do is maybe wheels and tires (if you are going to replace them). If you run spacers, you might want to get the 4/156 to 4/110 conversions because there are alot more wheel choices out there in the 4/110 pattern. 3rd, maybe a winch because you will want to test out your new tires. If you get heavier tires and wheels, you might want to look into a clutch kit with belt. After that, you can do what you want as far as performance, exc.