Dave, I am from an organ background and wouldn't know what to do with 76 keys . . . Have a 61 key version on the way.
John, I've played around with Korg stuff for a while and think the PA3X will offer a lot of mental challenge. Hopefully not too much for someone in their 80's. I like the wide range of editing available. But that kind of stuff also brings complex operating system software as well . . .
Marty, there are a couple of good Korg forums available. Will probably participate in at least one of them. See http://www.korgforums.com/forum/phpBB2/