The 17 year old SST18 is getting a bit long in the tooth & held together with pop-rivets & duct tape. I have been looking at two different possible replacements. One is an X384, it has the 48" deck & all wheel steering. The other is the ZTrak Z540R zero turn, probably with a 48" deck.
Mowing around the house is a mixed bag of terrain, lots of ins & outs but not much in the way of slopes (I use a 3pt finish mower behind the 1025R for about 1/3 mile of development road edge which drops off pretty quick to the ditch/woods). The SST18 handles it akk pretty well (not, of course, the steeper road edge areas - the front mounted engine would have it nose down in no time... )
The one thing that has me concerned about the ZTrak is the agri-fab Mow-n-Vac we use in the fall. If memory serves, the hitch for the Z500 series mentions a 250 lb. limit on towed items, the Mow-n-Vac is about 325 lb empty (at least that is the shipping weight).