I'm sure it will dig and will get get job done, but I honestly don't think the difference will be too significant better than your backhoe. Limitation factor is weight... that equipment probably weighs 2500-3000 LB. My L3301 with BH77 is around 5k LBs and I can dig a 3 foot deep trench (6 inch trench bucket) 60 feet long in about 2-3 hours. I probably could do 150 feet in 1 day, but that's going to probably wear my patience to operate the thing that long. If I hit rock, it wont go through it, but very hard compact soil it will (hard as in you'd need to use a pickaxe to go dig by hand). The backhoe is lifting the whole machine off the ground when I'm trying to dig the dense stuff or trying to rip a large root it pull the whole thing. If the weight was cut in half, I would be really disappointed...I need a lot trenching (150-175ft) at my place up north- very hard & rocky ground.
It is certainly not a commercial level machine, but it is at least 2 to 4 times more powerful than the B670 on my B7100.
I also plan on moving some big rocks out of a planned fence line. Lots of them are in the 100-200lb range, and a few are in the 2500lb range. I'll move what I can, then hire a big machine to move the rest.
Of course, there are always tree planting holes to dig, stumps to dig up, & culverts to clear.
If it works out, I may pull the BH off my tractor, and put the box blade back on.
And somewhere down the road, if I decide to sell it, I will probably double (or more) what I will have in it.
Equipment always sells high out here.
I do think it will do what you want, but I'd have expectations set on the size of tool. It's something that seems appropriate for garden work (redo a flow bed etc), but not long trenches...got what you're talking about, you really want something bigger...