<font color="blue"> but I have made up my mind that these tractors are too small for my wants. (Needs probably suited OK). </font>
This is a key consideration...
With one acre you probably don't want to go too big, and as said by Bob S and others above, you could get by with less than a BX/TZ sized tractor without problem. But you already know that. Your question is about tractor size to satisfy your wants rather than your needs.
So what I say will point at the "wants" issue... /forums/images/graemlins/smile.gif
There are members here who are happy with relatively large tractors on relatively small plots of land. I always think of Rick Jay, who has a B2910 on 2/3 acre, and loves it. Complete with loader and backhoe! Others have L series tractors on 5 acres, or maybe less.
Myself I have a B2910 TLB and BX2200 on 3.7 acres. Works for me! That's because my "Wants" most likely overcame my needs... /forums/images/graemlins/blush.gif
Anyway, if I understand your question, you want more than you need, but are not sure how much more than you need you want! /forums/images/graemlins/grin.gif
My advice would be to go one step larger than the BX.
The reasons include having more ground clearance (non issue probably), a more standard size 3PH (key consideration in my view), a bit stronger of a loader (can't hurt), option to add a factory backhoe later if you want to (most here love their little backhoes).
I have often thought that now, since I got most of the heavy work done around my place, that if I were to have only one tractor, the best fit would probably be a B7500 sized machine, whatever the current model number is.
That size machine is more tractor than the BX, but not too big and can cut grass pretty well.
The little machines are real tractors, but really are transition machines somewhere between lawn/garden tractors and CUTs.
I still have my old MTD garden tractor around and use it occasionally to pull a little cart. When I get on my BX, it feels more like the garden tractor than like my B2910 for some reason.
My opinion (best guess) is that you need no more than a BX (or less) but you want a B7500 sized machine, and not much (if any) more than that.