We are not talking about std turbos here though.
The way I see it is that if you are going to spend money to get over 400 then you might as well go for 500 - the cost is very similar as the big hit is getting that first foundation right.
Anything getting close to 400 on the std block, pistons etc is ultimately squeezing a safety margin. i got to 360 / 420 on the std turbo (& exhaust/filter) and I thought that was quick for a while.
The point with me showing the graphs was to put some facts out there for those that say you would actually lose performance, pick up, response etc. It is simply not the case. Sure there is a extra spool period on the larger turbos but this is only noticeable because the bit that comes afterwards is so ballistic. In the meantime you are still pulling away from a std spec or even remapped car.