If it was me, and if I wanted to stay with Yamaha, I'd be looking at a PSR-S910...lots of styles available for it at PSR Tutorial, including those from CVP and Tyros2/3/4.

Like you, I found the S950's audio based styles a waste...same as Tyros5's. If I didn't have my Tyros4, I would have picked up an S910...even lighter than an S950 BTW.

If you want to buy new, the PSR-S750 is essentially an S910 minus the Vocal Harmony/Mic Input.

Our buddy Bernie (Bernie9) is using an S910 as a more lightweight alternative to his Audya, so perhaps he can fill you in a bit more.

I hope things go well with your back, Deane, I've had issues with mine (old Martial Arts injuries), although not as serious as yours.

In any case, regarding keyboards, you'll get good advice here.

Ian