Husqvarna 54" I do our 2 acre yard in about 1.25 hours and that's going around tree's. They are a lot faster but if you turn it around as a zero turn you will dig up the grass on the slow turning wheel, at least I do at times.
That's a good size for that yard, I'm mowing about the same with a older 52in bobcat, and with trees and picking up the kids baseballs, I can do a good job in an hour an 15-30 minutes.
For 5k give or take you can get a nice 52in mower with kawasaki engine, welded deck and hydro transmission.
