If you don't wrench on your own saws, my recommendation would be to buy what you can get good service for. Good local service can more than make up for any initial price difference when things break.
Stihl and Husky both make good saws. I don't know much about Echo's. Look for a good local dealer with a good service reputation, ask them a lot of questions, and buy the one you're comfortable with.
As for the 400 vs the 562, Stihl's are always more expensive to begin with, but the 400 has about 1/2hp more and they're about the same weight. To the average homeowner that's probably nothing to even think about, but to professionals using it all day it's worth something.