Can you (or anybody else with a 1600p) tell me what it looks like when you play a game that has a max resolution of 1920x1200? Which I'm assuming is quite a few (at least the ones I play).
I can't imagine some mode that scales down the monitor to 1200p 1:1 or stretching it to the full width of the monitor looking that great. I remember some of the older Dell models not having a scaler built into it so you only had two options of the full native resolution, or like 800x600.
Put 1680x1050 on your current 1920x1200 screen. THAT is exactly what it's gonna look like. Slightly stretched, but nothing too serious. Not too noticiable in most games, unless you really look for it.
It would be horrible for desktop usage though.
Also, the games display the max resolution of 1920x1200 in your options since your current monitor can't do anything higher. With a 1600p monitor, you would see more options.
If I had an eyefinity resolution of 3240x1920, I would see every single official resolution 3240 or less lines of pixels wide and 1920 or less lines of pixels tall in the options.
Say a game that you think doesn't support 1600p? Because pretty much every game does.