You can't edit the sounds on a PSR740? That's tragic. I spend a fair bit of time tweaking sounds on my i30 - not that I need to, it's just a bad habit I've picked up I guess.
Yep, you're right about 'home' keyboards not being seen in bands 10 years ago. But, as a historical note, in 1960 it was a case of whatever piano happened to be in the venue, and some of those beasts were well past their appointment with the knacker's yard. So, via a Watkins 'Telstar', Hohner Pianet and a Hammond M103, here I am today with my Korg i30 and using it as the sole source on gigs in our duo (me and the missus). Rock on, young 'un, it's a long and happy road.