The Dremel 4000 might be a step up from the Dremel 300. Looks like it gets mixed reviews on Amazon.
As far as I can tell, the “electronic feedback” feature is an internal control to keep the spindle speed consistent. This would be a nice feature, since the Dremel 395 that we have will fluctuate in speed if other appliances are drawing power from the same circuit.
This rotary tool from Proxxon looks like it might be a good option as well, and is similarly priced.