It's not because Intel CPUs do not support 1920x1200 resolution. It's because 1920x1080 has grown in popularity over 1920x1200. Plus 1920x1200 are also more expensive so offering a 1920x1080 resolution screen also decreases the price tag.
You also need to provide a budget... and as stated above a graphic card's performance is more than just the amount of RAM it has. The graphic card model number is most important. For 1920x1080 resolution I recommend at least a nVidia GTX 670m if you want eye candy and performance.