Andy, I test mowed a Ferris IS500 yesterday,Its too bad that they opted for the Briggs and that they did NOT put in the cooling fans but the dealer is standing firm on the statement that overheating will not be a problem ???, he has to mean for the average homeowner.
I didn't like the IS500Z because it didn't have the cooling fans although my dealer told me the same thing as yours. I like the suspension, the pivoting front axle, and the heavy fabricated deck on my Ferris. If you can do without any one of these three, take a look at some of the Simplicity Zero turns. If I hadn't found the deal on the 1500 Ferris I probably would have bought the IS500Z Ferris or one of the Simplicities.