I have found out the the most intense game is with small quadrant, 6 races, no neutrals, High AI dificulty and medium AI bonus. It gets nasty long before getting cloaking tech.
This works best with Proportions, in which an Empire can lose every single colony, but as long it retains its homeworld there is chance to turn back the tide. I have found the hard way how easily a Homeworld can become an Stalingrad....
