I did that a few years ago with a PSRS900, in a Sunday Brunch setting. I still used my rolling stool, placed the keyboard and ultra-light stand on it, and rolled it in. One AC cord, plug in the mic and go!
I had tried using a Bose Compact, but they said it carried too far. I tried using Logitech Z2200s, but bass was too loud at the level I had to play. I unplugged everything, and they loved it, so that's what I used from then on. I stayed there for several months, every Sunday. Sometimes I wish I hadn't quit; it was the easiest job I ever had!
The S950 is even louder and could carry a slightly larger job.
I used it in a house party/reception one time and it worked great. Years before that, I used an arranger that ran on batteries at a wedding, where snow had knocked out the electricity. I don't remember which brand it was. It was in the infancy of arrangers!
Very few occasions I play that don't need more coverage though.
DonM