Couple of notes.
1. I also up-specc'ed to the MX5400 from the
L4701. You may not need to, but I'm glad I did. It's also a wider tractor, so more stability.
2. Make sure you account properly for the weight. The bare tractor weight does not tell the tale. By the time you add loader, bucket, brush hog, and loaded tires, well, in the case of my MX5400 that's nearly 4 tons (compared to the ~3700 lb bare weight). Add in two to three thousand pounds for the trailer, and now you're talking about substantial truck/towing power needs. My truck is only rated for 9000 lbs, so... I can't tow my setup with it unless I strip it down.
3. Kubota loaders, the number on the loader is the approximate weight it can lift (at the pin of course), in kilograms, so multiple by 2.2. Of course you may see far less than that depending on what you're lifting and how you're lifting it. In that one regard, if you're going to lift with a grapple and third function, gears may give you more lift, I find my grapple curiously weak, but you need to bear in mind you're sharing hydraulic function between the grapple, loader, and drive, and so if you're using more than one thing at a time, you're reducing power to the others. That said, I have HST and love it, but I wanted something simple. Note that I'm not saying you can't do two things at once with the hydraulics (as some people might claim). But it does affect your lifting capability if you're doing something really heavy. I have not had any problem with it while moving gravel and similar things though. It's the grapple, mostly that seems weak.
Side note: Messicks has a video showing that you can abuse your hydraulics with grapples and third functions, if you're not careful, resulting in potential damage. So think twice about using the grapple to try to lift out 1 ton rocks.