As you have seen, there is plenty of advise to be given on this board. And you have only seen a small fraction of it.

Even the smallest of the compact diesel tractors typically will be a giant leap in capabilities over what you are currently using. The kubota B7400/B7500, the BX series, and the larger B-series Kubotas will be leap years ahead of you current tractor, as well as the equivalents from the other colors (blue/green/etc).

These will be questions that you'll have to wrestle with:

(1) LOCAL DEALER SUPPORT: I believe this to be the strongest determination of which color to buy. If more than one color has good supporting local dealerships, then dive more into the "which color is better" arguments.
(2) 2wd or 4wd (4wd strongly recommended for resale value as well as increased usability).
(3) Gear drive or Hydrostat (overall I believe you'll like HST better)
(4) Live PTO? (You will want this feature; standard on HST transmissions)
(5) Tire type: Turf, Ag, or R-4s. (No strong recommendation here; maybe start looking at the type tire that you Power King has?)
(6) Rear or Mid Finish Mower? You'll either want a rear finish mower that you can swap out with the rotary mower (bush hog), or else you'll want a mid-mower than can be locked in the UP position (with the mid-PTO stationary) while simultaneously using the rear PTO for the rotary mower.
(7) Size and HP:
<font color=blue>I would like something somewhat larger than the little Power King, but not a whole lot larger.

Again, it would be used primarily as a lawn mower, but I now live in the country on sixteen acres of land, about 10 or 12 of which will need to be kept mowed (bush-hogged) to keep it from becoming overgrown with pine trees. </font color=blue>

These two statements seem contradictory. I will answer in terms of Kubota models with which I am familiar, but am not necessarily pushing Kubota. The BX2200 (22 hp diesel/3-point hitch/power steering/live PTO; will handle 60" mid-mower, optional front end loader (FEL), 4' rotary mower, etc) will probably be the compact tractor closest to the size of your Power King. The B2910 (and the newly introduced lower priced B7800) are at the top of the B-series (29 hp diesel; will handle a 60" or 72" mid-mower as well as a 5' rotary mower) sounds like the size tractor you should consider for size acreage you plan to mow.

Good luck. You have a hard yet enjoyable task ahead of you.