Not sure why you're not seeing them. They are available for all new Deere tractors. That being said, I prefer the X500 series because of the heavier transmission and the benefit of diff-lock. Unless you have a dead flat driveway, I would not consider anything else. If you buy a 300 series, and one wheel spins out, you're done. For that reason, we dont sell many snowblowers or blades on 300 series and under. In the X500 series, the X580 is much preferred due to having hydraulic lift and power steering. With the added weight of the snowblower on the front wheels, the mechanical steering can be a bit tougher than normal. Or if you have crushed stone and need to keep the blower up a bit to keep from digging in, youre not going to want to hold it up with your foot via the lift pedal. Hope this helps. Reach out to your local dealer.