I've had a 42" cut Troy-Bilt lawn tractor with a 17hp B&S engine for seven or eight years. Never had any trouble with it. They're also available with Kohler engines

If I were buying today, I'd probably go for the John Deere. Home Depot or Lowe's (I forget which) carries them at prices comparable to the Troy-Bilt line.

By the way, get a lawn tractor, not just a riding mower. And get some kind of cart to pull behind it. You'll probably discover you use it for hauling stuff around the property as much as you use it for mowing.