When I got my wheels for snows, steel wheels were not available. Just bought the cheapest alloy wheel. I did not get TPMS for the snows. Discount Tire Direct is the place I got my wheel/tire combo. Free shipping, mount/balance. When you get wheels and tires. Looks like they do have a 17" steel wheel now. Since the smallest wheel for MDX from factory is 18", I would not go smaller. My Tech came with 19" so I got 18". 17" could work fine, but I would not install it. Bolt pattern is 114.3
Here is their website, they have all kinds of offers, rebates, and if you get their Credit card, you get more discounts.