Sounds more like a "wife" justification rather than a plan but hey, whatever works!
P.S. I have played the Yamaha S250, Motif and others with the triple sampled piano and I think they are quite good. An interesting anecdotal story is that I actually have
a Kawai MP9000 piano. This has a great hammer touch and very nice piano sound. The model has been updated to the 9500.
My girlfriend is a classically trained pianist. She came with me one day to the music store when I was checking out the new Kawai to see if maybe it was worth upgrading. She tried the new Kawai, liked it just fine however, for comparison, she also tried the Yamaha as did I. She definitively choose the Yamaha over the Kawai stating that the Yamaha was "closer" to a real piano both in sound and feel.
Actually, after further discussion we both acknoweldged that the Kawai is closer to the feel of a Kawai piano whereas the Yamaha is closer to the feel of a Yamaha piano. Big surprise there! Anyway, she is Japanese and thus quite familiar with both bradns of piano. In Japan, Yamaha is the number one piano manufacturer and as far as she is concerened and, at this point I am also of the same mind,
the Yamaha P250 is an excellent rendition of a real piano. If the S90 has the same piano sound and feel, it would be the one to get.
This is, however the sticking point. I cannot find any information that says whether or not the piano in the S90, Motif Rack, or the P series are similar, the same, or whatever. I would like to know the differences, if any, but cannot find any source for that information.
So, choose wisely for this is truly a choice you will live with.