EL86's now sell for 2.90 at Antique Electronics. I'm planning to build a 18W with those. The tube has the same pinout as EL84 and is a bit more powerfull.

The data sheet information supplied by the tube manufacturers' design centers, list the typical operation of an audio output stage for a single 6V6 as producing about 5 W of continuous power, and a push-pull pair about 14 W. Amplifier manufacturers soon realized that the tube was capable of being used at ratings above the recommended maximums ...