Is it true that housing an odd number of finches together will cause aggression?

For example, I read that housing 3/5/7, etc finches together will cause aggression, and housing an even number (2/4/6, etc) will not. I have a Spice finch and Star finch and would like to introduce a Gouldian. The cage is 30x15 and I think 3 finches would be perfect. They would all be male, no females around to fight over.