TC18--
If by "grading" you mean cleaning things up and scooting some topsoil around, a boxblade will be much more useful than a rear blade; unless you're moving loose material, the rear blade will pretty much bounce around, and if you are moving heavy material, it will slough it off the sides. As both Wheeldog and Jai say, rear blades are not meant for moving dirt.
But if by "grading" you mean that you plan to change contours of the land or, as your profile suggests, enlarging your yard, you've got a real job ahead of you on 1.5 acres with your new TC18 and any implement. Ground engaging is the hardest work a tractor does, and factors of horsepower, traction, weight, and tread all come into play. As compared to a rear blade, the box blade's scarifiers make it possible at least to dig down a bit, but you still have to have the juice to dig in and pull the dirt around. In any soil (and especially clay like we have here in Ohio),this is a serious piece of work requiring serious equipment. Also, here, it's necessary to stockpile topsoil before doing any contouring; otherwise the good stuff ends up buried. Others may disagree, but I think that for any significant reshaping, hiring a pro to rough things in is well worth it, taking into account your time, having a project not drag on for ever, and wear and tear on your equipment. If a really skilled operator with a dozer or Bobcat can get the rough stuff done in half a day, that leaves plenty of finish work which is better-suited to a compact tractor.