Likewise, my Cub is great, but I'd prefer to go X5xx. That's a much beefier machine, with a K72 vs K62. Admittedly, 700 hours is a lot, not to mention it's accumulated VERY quickly. I'd wonder how they were used, at ~200 hours/year.
Any chance of finding a lower-hours Deere, even if the price climbed a bit?
There is a Deere X5xx I've heard about with some issues of a weak steering system. I'd want to check if it's this model. Definitely inquire in the Deere forum. But between the two, I'd rather have an X5xx, it's a "true" garden tractor.
Edit: And good call on replacing the S240 before the transmission gives out. If the hills are such that you're spinning the tires, then these are slopes that far exceed what it's built for.