It looks like you're going to be buying implements for a 55 HP cab tractor. That TYM weighs 4200# without loaded tires or the loader. If you're like 80% of members here, you'll load the rears, which gets you better traction and stability. So, with loaded tires and the loader, you're gonna be looking at a tractor in the 6000-6500# range.
Yes, a back blade is a chunk of metal, but yes, there is a big difference in quality. A higher quality blade will weigh considerably more. The added weight makes the unit cut much better and makes it much more durable. I don't know what the actual tread width will be on your rig, but you want a blade wider than your tire treads, I'd think you'll be looking at 6 or 7 foot models. Personally, I'd look for a used one. If you can find a decent deal, you'll be able to get a much more heavy duty blade that will be way more useful, much less likely to get damaged, and will always be worth what you paid for it, or a little more.
By the way, one of the only drawbacks to a larger tractor is that implements cost considerably more than for the smaller compacts.