I have a 4300 (FEL, BH,etc) and am still impressed with all the work it can do...and I have about 400+ hrs on it already. Glad you are happy with your purchse and it looks from your pics like you have been having a ton of fun!
Now, re the grading blade. I bought a yanmar 1500 this past fall that came with a small (about 5ft) rear blade. I have been amazed at what this little blade can do!...snow...dirt..... stones...it works very well.
If you want to do final leveling after bringing in fill/topsoil there is a better tool though. Drag an arena mat over the area several time in multiple directions. It moves a little dirt from high areas and fills low areas...just a little at a time. You can also use an old mattress spring or a section (about 10 foot) of chain link fence with a heavy bar at the front to hook up to your drag bar. The heavy front (steel, piece of 6 x 6 post, etc) distrubutes your tractors pull force as well as keeps the whole thing from "floating" too much. I did final leveling on 4acres for turf about 18 months ago...I used a friends arena drag mat and was trully amazed at how well it worked. It leveled significantly better than my dozer, blade, hand raking...even better that a rented rock hound.