You can run outside native resolution but the image won't be as good, it will be blurry.
If you are gaming, i would suggest WXGA+. 1920x1200 is too much for 9300 w/ 6800 unless you are planning to upgrade to 7800. With 1440x900 you can run full performance and have some eye candy. With 1920x1200 you can barely run the game with that resolution, and can't have stuff like AA/AF/soft shadows etc. In a year you probably have to decrease your native resolution in games anyway, so you will lose image quality, why go for higher resolution if you are going to decrease it anyway.
Also, WUXGA panel is glossy, it means you will be distracted by reflections if you are using it near a light source and it is very very difficult to use outdoors under the sun. With WXGA+ you won't have that problem.
It is kinda personal preference, both have their advantages/disadvantages. I think the price for WUXGA isn't worth it, so i went for WXGA+ and happy with it.