You mentioned that you want something bigger and more capable than the 5740, but really want the HST, and you missed the auto throttle of the HST+ when test driving.
This sounds a lot like what I've been mulling over for quite some time now. I looked at the specs of every HST tractor out there and not one of the standard CUT's has appreciably more lift capacity than I currently have, nor weight. (I have the same frame size and loader as you).
There is one tractor (not a typical CUT) that has impressive specs and enormous lift capacity, plus the HST+ and considerably more weight that seems like it would fit your needs.
Have you looked at Kubota's
M59 yet? It's a dedicated TLB with 3 point hitch and from the sounds of it, surpasses every other thing out there with HST. You can get it as a tractor/loader without the backhoe if you have no need for the backhoe.
Anyways, you may find that fits your needs better than any other tractors your looking at, plus it would be a serious upgrade from the 5740, not a lateral move.