If your budget is $400 there are many good display options; do you need your display for any specific reason like hardcore FPS gaming or causal gaming and movies?
Also, do not buy a 27" 1920x1080 monitor, the pixel pitch will be horrendous impacting the picture quality. The 27" ASUS you linked, for example has a pixel pitch of 0.311mm, you do not want this. The highest pixel pitch you should ever go is 0.27mm so lower = better.
i use a 40" lcdtv at 1920x1080p for movies, gaming, and the occasional web browsing or other general activity. while the pixel pitch may be higher than a 22" monitor of the same resolution this does not mean that it is a bad option. to say it is out of the question is EXTREMELY NAIVE. what you sacrifice in sharpness you gain in physical size. games look look great although first person shooters can be overwhelming on larger monitors!
you the buyer need to make the call if you dont mind giving up some image quality or sharpness for a larger monitor.
what you want to do with the monitor influences what you should buy.
all come into play.
for a generic recommendation for a $400 budget? i always recommend a 60hz e-ips from a major brand like asus, viewsonic, acer, etcetera. if you can get a 8bit p-ips, h-ips or s-ips for the price then i would go with that but normally they run outside your budget. i dont see the need for a 120hz tn panel unless of course you want 3d or believe that you will actually see a huge difference.