Thanks. Ogre3D and Irrlicht aren't full game engines, but UDK meets that criteria.
UDK's $99 + 25% of profits over $50,000 is perfect for a project such as this and as an engine it's certainly proven. Nice shaders out-of-the-box!
However, UDK's limitation of no OSX support without a prohibitively expensive license is not so good, nor the requirement to learn "special languages" Kismet and Unrealscript. I'm also quickly realizing their documentation is not upto Unity's standards, and they separate the programmer vs. level-designer workflow, an added cost when one does both.
Are those worth saving a couple grand if I self-publish? I'll go with "no" for now, but it was worth writing a couple scripts to check it out.