The same models are identical between the dealer and the box store. A D170 at the dealer is going to be exactly the same as a D170 at Lowes/HD. The box stores, however, only carry the low-cost line (D series).
The X300 series is the next step up, and is of much higher quality. Only a dealer sells the X300 (and X500 or X700). Of course, those tractors have a higher price.