The Ryohan is going to have a decent flush with double-cyclone bowl rinse. And it's gonna be available for 40% or more off list. But it's still expensive.
You might also look at the Aimes/Legato, which can be funky-ish particularly with the black seat.
The Ultramax II is a modern design as well. The Nexus is interesting, and you might look at the versions that have hand-painted decorations. (waza Miyabi)
The Aquia push-button dual-flush has a high degree of owner satisfaction...people love them.
Of course, for a real wow factor, any of the Neorest models would do. There is a G500 that's a washlet and integrated toilet that has a street price pretty close to what you would pay for the Ryohan: Model MS970CEMFG Comes with a bidet seat that lifts itself automatically, etc. That would be pretty impressive. But it's gonna take the whole 12" rough-in, so you need to be sure your flange is installed at least 12" from the finished wall and baseboard.