Thank You DNJ...No concerns at all...Just trying to learn about all arrangers I may like to own. I'm without one now...would Love to own a Genos may have to wait for sometime in the future. Trying to think if the 900X would work for now...If it had 76 keys I would jump on it ...I like piano work...Enjoy your EA-7  Sincerely Harold  
Hi  Harold,
Have a 73 note p121 connected to my sx900.  My set up is for home use, though.
At the moment use my laptop as an interface between sx and p121  ( p121 doesn’t have midi sockets only midi via USB) 
Works really well for me.  
I can play just piano.
I can play just using the sx900 keys .
I can play using p121 as controller. Mainly use this setup when I’m playing piano for melody.  For this setup, I use registrations and a pedal to take me thru the variations for a song. Basically don’t need to touch keyboard except to pick next song.
I don’t like stacked keyboard configuration , so my setup is L shape, that’s where the pedal and registrations come into their own.
I have monitor speakers so that the sound of sx is coming from the front ( behind piano, not from sx which is at the side.
In hindsight ,Genos wouldn’t have worked for me  anyway, I like fully weighted keys for piano.