One thing to keep in mind is that X plan, Supplier(GM), Affiliate Rewards(Dodge), are not always the cheapest, especially if they are having a sale. Those plans only work with factory rebates and not dealer rebates/discounts. If there are no sales going on they can be a nice price. 
For example, this weekend the local Ford dealer had a F350 4x4 Platinum for $13k off. It would actually be more expensive by about $3k to purchase by X plan because you would be losing out on the dealer discount. It pays to shop and know how these plans work because they are not always going to be in your favor. 
When Ram has their $12-14k off sales it is always going to be cheaper than using the AFF price.