While you can improve the suspension over stock, nothing you do will ever make it ride anything like an IFS suspension on those SXSs, so don't spend too much money trying to make it so, or you will be sorely disappointed. But don't think too negative about an old school bullet proof straight axle. I would argue that the straight axle is superior to the IFS for crawling where one wheel in up on a rock and the other wheel is down in a rut. The more you push one side up, the more the other side is pushed down, and you will never slam the frame down on the ground like an IFS. You might also try removing the sway bar as that will give you more of that travel offroad and help keep both tires on the ground at the expense of more body sway in hard corners on the pavement. But if you don't drive hard on the pavement, you will hardly notice it missing.