I have a John Deere Z225 42" mower and I'm not satisfied with the way it mows and mulches. I'm looking for something more powerful with around a 48" deck and closer to a commercial grade mower. I have about 3,500 to spend to upgrade. Any suggestions on what type of mower to get? Also, how many hours should I look to stay under on a used mower? I really need one that mulches/discharges the grass well. I'd really like to get an Exmark if at all possible. Thanks!