I can't decide between either the 27-inch: 2.7GHz or the 27-inch: 3.1GHz. Besides the .4 GHz different, the main difference looks to be the video card. 512 MB / 1GB. How well does the 2.7GHz handle games such as Steam? And for the 3.1 as well? And at full resolution/settings. Also will these machines chug if I get another 27" ACD as well? Maybe even down the line have 2 ACDs? And it's highly recommended to buy RAM from Crucial correct?