If I were you, I’d probably just go for the RZR S trim instead of the base and upgrading later, it’s usually cheaper and way less hassle to have the Fox shocks and long travel suspension from the start, especially if you’re planning on doing any serious trail riding. I’ve messed around with aftermarket power steering kits before, and while they work fine for the price, the factory EPS feels smoother and more reliable in the long run. As for brands, I’ve ridden a few different ones, and RZR feels more sporty and nimble, Can-Am rides a bit smoother and is more comfortable, and Yamaha is super reliable but maybe not as flashy. Really comes down to what kind of riding you want and how much you want to fuss with upgrades.