My best suggestion is to find the closest Home Depot that has a BX25 for rent and go rent it for a day or two. You will find out whether it has enough capability to do the work you need to do.
Great idea, Poopdeck! And it comes with a trailer so you can just hook up and go.
I have a BX25 on 25 acres and it is enough for me. Also, I would not be without the backhoe - I have it on all summer, and only take it off to put the snow blower on for the winter.
The BX25 is unlike any other SCUT in that it outperforms what you would expect - and by a lot! I was told by dealers that it was made for heavy construction-like work, and it has done very well for me. It also fits nicely in my garage, although you need to make sure you have an extra high OH door so you don't need to fold the ROPS down each time you put it away. (I have 8 ft.)
There are two limitations that have been a bit of a pain for me. The first is the lift capacity. (Only 745 lbs. or so at the pivot pin compared to a whopping 1700 lbs for that LS on the YouTube video.) However, that has only rarely been a serious impediment for me. (I can still fill the FEL to the brim with almost anything, even with the BXpanded.com bucket expander and carry it around, the only exception so far being wet sand.)
And the second is the digging capacity with respect to the backhoe. I have very rocky, sandy soil, and I would never try digging any deep ditch because the rocks would just make it take forever. (I had to dig a 5-foot, 100' long ditch for a new water line a while ago, and I just hired a full-sized backhoe for about $250 to do it.) But in your case, the BX25 backhoe would do just fine digging up to 6' or so, since as you said most of your soil has no rocks.
Another big consideration as was mentioned before is the space for moving around. Do you have the room for a bigger tractor? I have used my BX25 in a lot of tight spaces where it just BARELY fit, and where anything bigger could simply not have done the job.
Again, it would be a great idea to rent a BX25 from Home Depot and try it out. And do keep us posted!
James