personally i would prefer portrait instead of landscape since you keep a widescreen view without going into an ultra ultra widescreen view. keep in mind that not all games might support strange formats like that though (either).
also keep in mind that 3x the resolution is going to be very demanding on a card. especially on any brand new games requiring alot of video card power. i dont use ati cards so i cannot tell you how it would perform... check toms charts.
3x27 might be too big. 3x24 is going to be pretty big as well. you could get away with 3x22 and be fine.
what is out there? look into the different panel types. personally i prefer to use nothing less than 8-bit ips screens as they are considered the best in terms of image quality. look through the forum and you will find tons of information on this topic.