While awesome, I doubt many Paradox fans have the luxury of having two monitors.
On that note, however, it would be useful if you could have different portions of the map on different screens. Say, Normandy on one and New Guinea on the other.
I have a 2400 x 1600 desktop at work - two 21" monitors rotated 90 degrees arranged side by side.
This is a function of the NVidia graphics card, and any program should run on it.
But it makes no difference how big the screen area is, if the program is designed for parts of the UI to always overlay each other. FE for the Production screen to alway open on top of the map. Unless Paradox design the interface where each part opens in a separate window that you can drag to another part of the screen, then you are stuck with the map being covered.
But the bigger the area you have, the more map area you can see at any one time, up to the limitations of the program. The only benefit of a really massive screen area is if you run HOI3 in a window instead of full screen (if possible, never tried this with EUIII) and then you can also have your other apps available on screen at the same time.