Tried to delete my question. I had asked about the differences in the decks on the 900 series but the JD site does a great job of explaining. I think we are going to give the 915E a shot. We have relatively flat ground and it's far from golf course quality so lack of rear anti scalp wheels not an issue. Like to have them-but then a 920M is $1500 more. Our dealer shot us a price under 8k for a new 915e with 54" deck and iso seat. I like Kohler motors and realize they smoke. Years ago I had a JD lawn tractor with a 25hp Kohler. Worked great!Got a 997 with the 72" deck, 31 HP Yanmar diesel engine, only problem with the 997 it's a heavy sucker with the diesel, right around a ton.
I doesn't like wet or damp ground.
Really don't have scalping problems, normally mow at the 3 or 3 1/4 height position, gives a great looking finish cut at full tilt, 11 - 12 MPH.
Would imagine a gasoline job at 31 HP should do the same and be a little lighter.