I just got my BX1800 a couple weeks ago. The box is the rear ballast box and I believe they are about $150-$175 (I can't remember exactly). I intended to add some gravel, or cinder blocks etc. but when I went to get my cinder blocks the other night, I realized I have the boat trailer blocked up with them for the winter. So still wanting some rear ballast(as recommended by many on this forum many times)I put the one cinder block I had in, and added a couple bags a mulch we had in the shed.
I didn't get my tires loaded, and haven't used it enough yet to decide if that was a good or bad idea. I figured with the rear ballast box, I wouldn't need to and it would be easier for mowing wthout.
Overall, I did have the loader quite full a few times and the rear felt a little light, but I figured I would definately be ok with more weight added once I either put the cinder blocks in or buy some bags of gravel.
As for hauling things around, I really wish the BX had a tool box of some sort. I think I may end up adding one as some others have done.
The rear box, could be insulated and a favorite beverage as well as ice could be added during the hot weather. There are even 4 drain holes that would accomodate melt water......or I guess you gould use it as a tool box. Your call!