That's good input from everyone. I had considered HST and I understand its advantages but I found myself liking the gear better. It is strange even to me as I never learned how to drive a stick car. It just felt good cruising around the dealers lots. The 2540 is probably adequate for my needs but I think its too light. The 2555 has all the features I want but more horsepower than I need. The 5545 is bigger than I need. If I had the option to pick and choose I'd take the 2555 frame with a 40 hp engine in it. It seems odd that the 2500 series has more than one frame size in it. I'm also RPM sensitive. I don't like these high RPM diesel engines. To me there is something wrong with that. I believe the Yanmars are rated up at 2800 RPM. To me that signals the engine doesn't have any torque. Right or wrong, that's how I feel. The 2650 RPM PTO speed of the 2540 annoys me. The 2555 is at 2300 and the 5545 is down at about 2100. Part of my standard test drive is tilling. Get the RPM up to PTO speed and put it in first gear low to see how it sounds and feels.
The 5545 is the direction I'm leaning. From all my reading, heavier does seem to be better. Looking carefully at the unit you can see where the weight is: added support, bigger pieces, thicker pieces. It will mean 7' implements which have a nasty jump in price over the 6' versions. Mower, tiller and box blade and rake for now. A plow for next winter. Maybe next year I might look at cultivator, disc and a cultipacker.