Out of all the "Amps" out there for keyboards, the Fender SFX 200 is still my favorite for small gigs.
http://www.harmony-central.com/Events/SNAMM98/Fender/SFX-Amplifier-Technology.html

It has enough juice for medium venues, true stereo, nice effects, and is easy to move around on wheels.

The way the implemented the stereo is kind of quirky. If you look at the photo at the above site, you will see a 10 inch speaker angled at 90 degrees on the bottom and on the top you have a 12 inch with a Piezo high frequency speaker. This gives great stereo effects plus you can also use it for vocals and it has built in effects for vocals and Guitar.

I've had mine for 4 years now and it still pleases me.

Al