Do not forget that all those calculators consider 100% uptime, which never happens. Calculating 90% to 95% uptime is much more reasonable, I'd recommend to insert 360GH/s as hashrate for a 400GH/s unit in order to factor possible downtime.
Agreed but 90% would be a bit extreme. 95-97% would be good numbers. There's also the possibility of KNC overdelivering - 500gh/s instead of 400gh/s???
Anything above 400gh/s and we will do really good.