And the last word on this...
I started using the new super-duper PC in earnest today. And I've already discovered that if I use the monitor in portrait mode for lengthy periods I get a crick in the neck! It's literally too high - if I'm in my normal seat position and turn the screen around to portrait the top is about 3" above my eyes. There are ways to fix this, of course, by e.g. raising the seat or leaning back, but I'll mostly be reserving portrait mode for final layout checks etc., I think.
