AK:
First, I have 0 experience with Simplicity, so no help there. What I can tell you is that last summer I sold a Husqvarna YT42DXLS lawn tractor which I loved but kept having problems with tranny brackets breaking. It had an automatic locking differential - which I really need here. I think that was a 18.5 HP Kohler engine. Anyway, I bought a new Deere X-370, 20 HP Kawasaki engine, power steering (Oh God that's nice!), hydraulic deck lift, armrests, bumper, and 2 45# weights to compensate for loss of the locking diff. Over 6K, but I love it!!!
Which brings me to the point I want to make: although it's running perfectly and in great shape, it burns twice the gas the Husky did - about 1 gal./hr. Of course, I mow a rough, hilly, somewhat rocky 1.5 acres, and with 90# of weight on the back plus my 160#, so some increased gas use was expected. I can live with it cause I really like the tractor. Point is though, if you're gonna get a 23 HP Kawasaki engine on that even larger X-380, you can expect pretty heavy fuel consumption. Just sayin'. It will likely be, like for me, no real concern to you. And, again, I love it, even if it does have a drinking problem!