If you look at the bottom of the Husqavarna page, they list all their tractors.
(not recommending them, just using them as an example)
http://www.husqvarna.com/us/products/riding-lawn-mowers/
Note that, except for the first one, a lot of them look the same.
Same frame, just different engine, and different width deck.
Choose the width you need, then choose the engine / tranny combo you want.
Note that the wider widths tend to stick out from between the wheels...
I always put on a mulching kit, and that takes a little more power, so i go up one model, and get the bigger engine.
First thing, I paint the deck with some truck bed liner paint, being careful of the moving parts, and blade width...
If you mowing a lot, a frame rail oil cooler and oil filter sandwich adapter may be a good buy.
https://www.etrailer.com/Transmission-Co...CFdqLswodzQsNEg
Slime (not the aerosol can, the bottle) in the tires, an oversized filter, if possible, and happy mowing...